From: Martin Schwidefsky <schwidefsky@de.ibm.com>

Core s/390 changes:
 - Add -mbackchain to CFLAGS to prepare for gcc 3.4 with comes with a
   default setting of -mno-backchain
 - Add implementation of strcpy.
 - Pad bytes after string end in strncpy.
 - Fix __sem_update_count inline assembly for gcc 3.4.
 - Export smp_ptlb_all for tlb flushing in module code.
 - Fix sched_clock.
 - Remove the last KERNEL_VERSION #if in s390 code.
 - Add dummy implementation for missing dma_{alloc,free}_coherent.
 - Avoid cast of lvalue in idal_buffer_{from,to}_user.
 - Remove _exit definition from unistd.h.