Merge any from the trunk.

svn path=/branches/release/libs/any/; revision=83013
Merge Boost.Any from trunk (fixes #6999)

svn path=/branches/release/libs/any/; revision=84086
Docs update: ValueType of Boost.Any shall be CopyConstructible, not Move constructible (refs #6999)

svn path=/branches/release/libs/any/; revision=84603