Decode /dev/loop ioctls

Decode /dev/loop ioctls

Needed to debug some losetup failures, and it's easier when you can see
what the kernel is getting vs what you think you're sending, so add some
decoders for those ioctls.

* loop.c: New file.
* Makefile.am (strace_SOURCES): Add loop.c.
* defs.h (loop_ioctl): New prototype.
(string_quote): Likewise.
* ioctl.c (ioctl_decode): Call loop_ioctl when code is 'L'.
* util.c (string_quote): Remove static keyword.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>