move signal.h REG_* macros under _GNU_SOURCE protection
[musl] / arch /
drwxr-xr-x   ..
drwxr-xr-x - arm
drwxr-xr-x - i386
drwxr-xr-x - microblaze
drwxr-xr-x - mips
drwxr-xr-x - powerpc
drwxr-xr-x - x86_64