s390: vfork support

vfork support for s390/s390x.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/usr/klibc/SYSCALLS.def b/usr/klibc/SYSCALLS.def
index cfda87d..a9dd006 100644
--- a/usr/klibc/SYSCALLS.def
+++ b/usr/klibc/SYSCALLS.def
@@ -28,7 +28,7 @@
 ; A lot of architectures need architecture-specific vfork
 ; stubs, due to the no-stack requirement.  These are the
 ; architectures which do not.
-<alpha,m32r,ppc,ppc64,sh> pid_t vfork()
+<alpha,m32r,ppc,ppc64,sh,s390,s390x> pid_t vfork()
 <sparc,sparc64> pid_t vfork@forkish()
 #endif
 <!alpha> pid_t getpid()