selinux-h: add stubs and wrappers for raw counterparts
Add stubs and wrappers of already covered libselinux interfaces for
their `raw` counterparts. These counterparts perform the same
operation expect for context translation. Context translation is used
to convert SELinux MCS/MLS labels into human readable form, see
mcstransd(8).
* lib/se-selinux.in.h: Add declarations for raw variants.
* lib/se-label.in.h: Likewise.
* lib/getfilecon.c: Add wrappers for problematic raw variants.
* m4/selinux-selinux-h.m4: Use wrappers for problematic raw variants.