Add better error checks in mutex support, see https://svn.boost.org/trac/boost/ticket/8903
Fix typos from https://svn.boost.org/trac/boost/ticket/9283 and update history.
BREAKING CHANGE: change mark_count to do what's documented (and what the std does).
See https://svn.boost.org/trac/boost/ticket/9227.
Fix for std::locale's which produce collate keys with embedded null's, see https://svn.boost.org/trac/boost/ticket/9451
Fix GCC test compiles with exception handling disabled.
Update history and version number, regenerate docs.
Fix generic mutex usage, see https://svn.boost.org/trac/boost/ticket/9461.
Add checks for invalid UTF-8 sequences, see: https://svn.boost.org/trac/boost/ticket/9473
Fix no-exception handling build with GCC.
Tentative fix for case where a transformation of a NULL string is requested.
Merge branch 'develop' of https://github.com/boostorg/regex into develop
Revised tentative fix for VC11/12 failures which occur when calling wcsxfrm for "\0".
Merge branch 'develop'