This only change the cxx11 basic_string, because COW strings don't
correctly propagate allocators anyway.
2019-05-30 Nina Dinka Ranns <dinka.ranns@gmail.com>
LWG2788 basic_string spurious use of a default constructible allocator
* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
(basic_string::_M_replace_dispatch): Construct temporary string with
the current allocator.
* testsuite/21_strings/basic_string/allocator/char/lwg2788.cc: New.
* testsuite/21_strings/basic_string/allocator/wchar_t/lwg2788.cc: New.
From-SVN: r271789
