[PATCH] mutex: some cleanups

Turn some macros into inline functions and add proper type checking as
well as being more readable.  Also a minor comment adjustment.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>