Make sure the value in abs() does not get truncated if it is greater than 2^32

abs() will truncate the input if is it outside the 2^32 range.  Fix that
by assuming `long' input.

This might generate worse code in the common case.

Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>