Unordered: Merge from trunk.

Anotehr overhaul. Can now use `void_pointer` for links between nodes, although
it doesn't as I don't think `void_pointer` support is strong enough in existing
allocators.

Also no longer relies on using base pointers for custome pointer types.  And
scaled back member function detection to just detect if an allocator has a
member, not what its signature is. I found that the trait could be confused by
ambiguous overloads. This might be fixable.

Better documentation of C++11 compliance to come.


[SVN r74859]

test/exception/Jamfile.v2

@@ -14,9 +14,9 @@ project unordered-test/exception-tests
         <toolset>intel:<warnings>on
         <toolset>gcc:<cxxflags>"-pedantic -Wstrict-aliasing -fstrict-aliasing -Wextra -Wsign-promo -Wunused-parameter"
         <toolset>darwin:<cxxflags>"-pedantic -Wstrict-aliasing -fstrict-aliasing -Wextra -Wsign-promo -Wunused-parameter"
-        <toolset>gcc:<define>_GLIBCXX_DEBUG
+        #<toolset>gcc:<define>_GLIBCXX_DEBUG
         #<toolset>darwin:<define>_GLIBCXX_DEBUG
-        <toolset>msvc:<warnings-as-errors>on
+        #<toolset>msvc:<warnings-as-errors>on
         #<toolset>gcc:<warnings-as-errors>on
         #<toolset>darwin:<warnings-as-errors>on
     ;