tools/vm/page-types.c: add memory cgroup dumping and filtering

This adds two command line keys:

 -c|--cgroup path|@inode	Walk only pages owned by this memory cgroup
 -C|--list-cgroup		Show memory cgroup inodes

[vdavydov@virtuozzo.com: opt_cgroup should be uint64_t.  Fix conflicts with "tools/vm/page-types.c: support swap entry"]
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>