[PATCH] s390: sigcontext.h vs __user

Add an include of linux/compiler.h in sigcontext.h to avoid compiler errors in
user space apps because of a missing definition for __user.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>