* include/bits/c++config (_GLIBCXX_USE_WEAK_REF): New.
(_GLIBCXX_TXN_SAFE, _GLIBCXX_TXN_SAFE_DYN): Use _GLIBCXX_USE_WEAK_REF
and move after its definition.
* config/os/aix/os_defines.h (_GLIBCXX_USE_WEAK_REF): Override.
* src/c++11/cow-stdexcept.cc: Use _GLIBCXX_USE_WEAK_REF instead of
__GXX_WEAK__, and only provide transactional clones if
_GLIBCXX_USE_WEAK_REF is true. Don't provide stubs of libitm
functions.
From-SVN: r232539
9585381acd