Merge changes from Trunk.
Fixes #6013.
Fixes #7151.
Fixes #7359.
Fixes #7389.
Fixes #7452.
Fixes #7528.
Fixes #7703.
Fixes #7841.
Fixes #7898.
Fixes #7938.
Fixes #8048.

svn path=/branches/release/boost/config.hpp; revision=83139