Merge unordered from trunk.

- Avoid using operator& with the value type.
- More comments in headers.
- Remove old clang workaround.
- Adjust use of inline to make Borland a little happier.
- Avoid `-Wconversion` warnings.


[SVN r67663]

doc/Jamfile.v2

@@ -3,6 +3,9 @@
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
+using boostbook ;
+using quickbook ;
+
 path-constant images_location : ../ ;
 path-constant admonishment_location : ../../../../doc/src/images ;