[SystemZ][z/OS] Missing locale functions libc++

The aim is to add the missing z/OS specific locale functions for libc++ (newlocale, freelocale and uselocale).

Reviewed By: ldionne, #libc, curdeius

Differential Revision: https://reviews.llvm.org/D98044

GitOrigin-RevId: ebe6161c54b92199d897d086834e0c873e3de01c
5 files changed