Add ptr_to_compat() to s390 - needed by the new robust-futex code.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>

untested. CHECKME: am i right about the 0x7fffffffUL masking?
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>