Added documentation for advance and distance. Various cleanup and fixes.

- Fixed multiple broken links to the documentation. Converted some of the
  links to internal references to the QuickBook documentation. Not all
  links converted because some of the QuickBook pages are not completely
  converted.
- Renamed utilities.qbk to type_traits.qbk and removed the part duplicated
  by concept_checking.qbk.
- Renamed traits.qbk to iterator_traits.qbk to better disambiguate with
  other type traits documented in type_traits.qbk.
- Converted some of the headings in iterator concepts to sections to be
  able to give those sections ids. This allows to reference those sections
  from other places in the documentation.
- In order to preserve the more compact pagination of the new sections
  (i.e. to have multiple sections on one page, like it was with headings)
  set chunk.section.depth=2 in the docs Jamfile.

doc/quickbook/iterator.qbk

@@ -29,7 +29,10 @@
 
 [/  Links   ]
 
-[def _iterator_           [@../../libs/iterator/doc/index.html Boost.Iterator]]
+[def _iterator_           [@../../../iterator/doc/index.html Boost.Iterator]]
+[def _concept_check_      [@../../../concept_check/index.html Boost.ConceptCheck]]
+
+[template sub[x]'''<subscript>'''[x]'''</subscript>''']
 
 [section:intro Introduction]
 
@@ -71,19 +74,23 @@ and a _GOTW_50_.  New-style iterators go well beyond
 patching up `vector<bool>`, though: there are lots of other
 iterators already in use which can't be adequately represented by
 the existing concepts.  For details about the new iterator
-concepts, see our [@./new-iter-concepts.html Standard Proposal for New-Style Iterators].
+concepts, see our [@../new-iter-concepts.html Standard Proposal for New-Style Iterators].
 
 [h2 Iterator Facade and Adaptor]
 
-[def _facade_ [@./iterator_facade.html facade]]
-[def _adaptor_ [@./iterator_adaptor.html adaptor]]
+[/
+[def _facade_ [link iterator.generic.facade facade]]
+[def _adaptor_ [link iterator.generic.adaptor adaptor]]
+]
+[def _facade_ [@../iterator_facade.html facade]]
+[def _adaptor_ [@../iterator_adaptor.html adaptor]]
 
 Writing standard-conforming iterators is tricky, but the need comes
 up often.  In order to ease the implementation of new iterators,
 the Boost.Iterator library provides the _facade_ class template,
 which implements many useful defaults and compile-time checks
 designed to help the iterator author ensure that his iterator is
-correct.  
+correct.
 
 It is also common to define a new iterator that is similar to some
 underlying iterator or iterator-like type, but that modifies some
@@ -92,9 +99,9 @@ library supplies the _adaptor_ class template, which is specially
 designed to take advantage of as much of the underlying type's
 behavior as possible.
 
-Both _facade_ and _adaptor_ as well as many of the `specialized
-adaptors`_ mentioned below have been proposed for standardization 
-([@./facade-and-adaptor.html Standard Proposal For Iterator Facade and Adaptor]).
+Both _facade_ and _adaptor_ as well as many of the [link iterator.specialized specialized
+adaptors] mentioned below have been proposed for standardization
+([@../facade-and-adaptor.html Standard Proposal For Iterator Facade and Adaptor]).
 
 [h2 Specialized Adaptors]
 
@@ -103,15 +110,15 @@ iterator templates based on the Boost [link
 iterator.intro.iterator_facade_and_adaptor iterator facade and adaptor]
 templates.
 
-[def _counting_    [@./counting_iterator.html         `counting_iterator`]]
-[def _filter_      [@./filter_iterator.html           `filter_iterator`]]
-[def _function_    [@./function_output_iterator.html  `function_output_iterator`]]
-[def _indirect_    [@./indirect_iterator.html         `indirect_iterator`]]
-[def _permutation_ [@./permutation_iterator.html      `permutation_iterator`]]
-[def _reverse_     [@./reverse_iterator.html          `reverse_iterator`]]
-[def _shared_      [@./shared_container_iterator.html `shared_container_iterator`]]
-[def _transform_   [@./transform_iterator.html        `transform_iterator`]]
-[def _zip_         [@./zip_iterator.html              `zip_iterator`]]
+[def _counting_    [link iterator.specialized.counting `counting_iterator`]]
+[def _filter_      [link iterator.specialized.filter `filter_iterator`]]
+[def _function_    [link iterator.specialized.function_output `function_output_iterator`]]
+[def _indirect_    [link iterator.specialized.indirect `indirect_iterator`]]
+[def _permutation_ [link iterator.specialized.permutation `permutation_iterator`]]
+[def _reverse_     [link iterator.specialized.reverse `reverse_iterator`]]
+[def _shared_      [link iterator.specialized.shared_container `shared_container_iterator`]]
+[def _transform_   [link iterator.specialized.transform `transform_iterator`]]
+[def _zip_         [link iterator.specialized.zip `zip_iterator`]]
 
 [def _shared_ptr_  [@../../smart_ptr/shared_ptr.htm `shared_ptr`]]
 
@@ -133,7 +140,7 @@ templates.
 
 * _reverse_: an iterator which traverses the elements of some
   bidirectional sequence in reverse.  Corrects many of the
-  shortcomings of C++98's ``std::reverse_iterator``.
+  shortcomings of C++98's `std::reverse_iterator`.
 
 * _shared_: an iterator over elements of a container whose
   lifetime is maintained by a _shared_ptr_ stored in the iterator.
@@ -141,7 +148,7 @@ templates.
 * _transform_: an iterator over elements which are the result of
   applying some functional transformation to the elements of an
   underlying sequence.  This component also replaces the old
-  ``projection_iterator_adaptor``.
+  `projection_iterator_adaptor`.
 
 * _zip_: an iterator over tuples of the elements at corresponding
   positions of heterogeneous underlying iterators.
@@ -150,9 +157,9 @@ templates.
 
 [h3 Traits]
 
-[def _pointee_          [@./pointee.html         `pointee.hpp`]]
-[def _iterator_traits_  [@./iterator_traits.html `iterator_traits.hpp`]]
-[def _interoperable_    [@./interoperable.html   `interoperable.hpp`]]
+[def _pointee_          [link iterator.utilities.traits `pointee.hpp`]]
+[def _iterator_traits_  [link iterator.utilities.iterator_traits `iterator_traits.hpp`]]
+[def _interoperable_    [@../interoperable.html   `interoperable.hpp`]]
 [def _MPL_              [@../../mpl/doc/index.html   [*MPL]]]
 
 * _pointee_: Provides the capability to deduce the referent types
@@ -163,14 +170,15 @@ templates.
   retrieve an iterator's traits.  Also corrects for the deficiencies
   of broken implementations of `std::iterator_traits`.
 
-[\ * |interoperable|_ (PDF__): Provides an _MPL_ compatible metafunction for
-     testing iterator interoperability
+[/
+* _interoperable_: Provides an _MPL_ compatible metafunction for
+  testing iterator interoperability
 ]
 
 [h3 Testing and Concept Checking]
 
-[def _iterator_concepts_  [@./iterator_concepts.html `iterator_concepts.hpp`]]
-[def _iterator_archetypes_  [@./iterator_archetypes.html `iterator_archetypes.hpp`]]
+[def _iterator_concepts_  [link iterator.concepts `iterator_concepts.hpp`]]
+[def _iterator_archetypes_  [link iterator.utilities.archetypes `iterator_archetypes.hpp`]]
 
 * _iterator_concepts_: Concept checking classes for the new iterator concepts.
 
@@ -182,8 +190,16 @@ The library provides a number of generic algorithms for use with iterators. Thes
 algorithms take advantage of the new concepts defined by the library to provide
 better performance and functionality.
 
+[def _advance_          [link iterator.algorithms.advance `advance.hpp`]]
+[def _distance_         [link iterator.algorithms.distance `distance.hpp`]]
 [def _next_prior_       [link iterator.algorithms.next_prior `next_prior.hpp`]]
 
+* _advance_: Provides `advance()` function for advancing an iterator a given number
+  of positions forward or backward.
+
+* _distance_: Provides `distance()` function for computing distance between two
+  iterators.
+
 * _next_prior_: Provides `next()` and `prior()` functions for obtaining
   next and prior iterators to a given iterator. The functions are also compatible
   with non-iterator types.
@@ -208,9 +224,9 @@ better performance and functionality.
 
 [include concept_checking.qbk]
 
-[include traits.qbk]
+[include iterator_traits.qbk]
 
-[include utilities.qbk]
+[include type_traits.qbk]
 
 [endsect]
 
@@ -280,4 +296,3 @@ library you see today.
 
 [endsect]
 
-