[patch] libstdc++/69386 Ensure C++ language linkage in cmath and cstdlib

[Dominique d'Humières]

Jonathan,
>     PR libstdc++/69386
>     * include/c_global/ccomplex: Ensure C++ language linkage.
>     * include/c_global/cmath: Likewise.
>     * include/c_global/cstdlib: Likewise.
>     * include/c_global/ctgmath: Likewise.
>     * testsuite/17_intro/headers/c++2011/linkage.cc: New.

The test  testsuite/17_intro/headers/c++2011/linkage.cc fails on darwin

/opt/gcc/work/libstdc++-v3/testsuite/17_intro/headers/c++2011/linkage.cc:47:19: fatal error: uchar.h: No such file or directory

TIA

Dominique