Merge Boost.Build from the trunk.

git-svn-id: http://svn.boost.org/svn/boost/branches/release@84398 b8fc166d-592f-0410-95f2-cb63ce0dd405
Add type_erasure to release

git-svn-id: http://svn.boost.org/svn/boost/branches/release@84399 b8fc166d-592f-0410-95f2-cb63ce0dd405
atomic: merge fixes from trunk



git-svn-id: http://svn.boost.org/svn/boost/branches/release@84400 b8fc166d-592f-0410-95f2-cb63ce0dd405
lockfree: merge fixes from trunk 



git-svn-id: http://svn.boost.org/svn/boost/branches/release@84401 b8fc166d-592f-0410-95f2-cb63ce0dd405
Merge root index file.

git-svn-id: http://svn.boost.org/svn/boost/branches/release@84413 b8fc166d-592f-0410-95f2-cb63ce0dd405