Convert the unsafe signed (16bit) used_math to a safe and optimal
PF_USED_MATH

I might have broken arm, see the very first change in the patch to
asm-offsets.c, rest looks ok at first glance.

If you want used_math to return 0 or 1 (instead of 0 or PF_USED_MATH), just
s/!!// in the below patch and place !!  in sched.h::*used_math()
accordingly after applying the patch, it should work just fine.  Using !!
only when necessary as the below is optimal.

From: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>

This patch had fixed restore_sigcontext/restore_sigcontext32 about MIPS.
Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>