More ls -Z upgrading. Move TOYBOX_SELINUX and TOYBOX_SMACK support from

More ls -Z upgrading. Move TOYBOX_SELINUX and TOYBOX_SMACK support from
portability.h to new lib/lsm.h. Update ls.c to use it.

Fix "ls . toys" (two directories when one is . or ..), which was filtering
out the . as something we shouldn't recurse into even though it was explicitly
listed on the command line. For some reason "ls -Z . toys" is still segfaulting
though (but "ls -Z ." isn't), need to figure out why...