* spu/jsre.h: Add JSRE_SCHED_YIELD, JSRE_UMASK, JSRE_UTIME, and
JSRE_UTIMES.
* spu/sched_yield.c: New file add sched_yield via assist call.
* spu/umask.c: New file add umask via assist call.
* spu/utime.c: New file add utime via assist call.
* spu/utimes.c: New file add utimes via assist call.
* spu/Makefile.in: Add new files.