uwrap: Reflect changes of list of supplementary group IDs to main process.

When thread changes supplementary group list, this change must be
reflected to main process.

Difference between syscall and libc call must be preserved.

Signed-off-by: Robin Hack <hack.robin@gmail.com>
Merge branch 'master' of github.com:marmolak/uid_wrapper

Conflicts:
	src/uid_wrapper.c