Merged changeset 85793 from trunk.

git-svn-id: http://svn.boost.org/svn/boost/branches/release@85969 b8fc166d-592f-0410-95f2-cb63ce0dd405
Default initialization for vector-like containers
Complexity guarantees for associative container constructors and ordered input ranges
Fix for #9166
Added benchmark for associative containers
Removed check for old MSVC compilers and #pragma once.

git-svn-id: http://svn.boost.org/svn/boost/branches/release@85970 b8fc166d-592f-0410-95f2-cb63ce0dd405