Fixes #10520 in Boost Trac
Removed some unused preprocessor includes
Updated changelog with ticket #10520
Fixed #10469: Erasing from intrusive unordered_multiset with optimize_multikey goes into an infinite loop
Updated changelog with #10469
Removed unused variables warnings.
Header dependency cleanup. Removed some standard includes, splitted large "utilities" headers, and minimized algorithm dependencies.
Fixed reverse_iterator's relational operators