PR c++/81852 define feature-test macro for -fthreadsafe-statics
gcc/c-family:
PR c++/81852
* c-cppbuiltin.c (c_cpp_builtins): Define __cpp_threadsafe_static_init.
gcc/testsuite:
PR c++/81852
* g++.dg/cpp1y/feat-cxx11.C: Check __cpp_threadsafe_static_init.
* g++.dg/cpp1y/feat-cxx14.C: Likewise.
* g++.dg/cpp1y/feat-cxx98.C: Likewise.
* g++.dg/cpp1y/feat-neg.C: Likewise.
* g++.dg/cpp1z/feat-cxx1z.C: Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251939 138bc75d-0d04-0410-961f-82ee72b054a4