mmap/mmap14.c: new case to test MAP_LOCKED of mmap

Create test case for MAP_LOCKED of mmap.

Verify pages are locked by checking section "VmLck" of /proc/<pid>/status.

Signed-off-by: DAN LI <li.dan@cn.fujitsu.com>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Jan Stancek <jstancek@redhat.com>