* libc/sys/linux/shm_open.c: New file.
* libc/sys/linux/shm_unlink.c: Ditto.
* libc/sys/linux/Makefile.am: Add support for shm_open.c and
shm_unlink.c.
* libc/sys/linux/Makefile.in: Regenerated.
* libc/sys/linux/sys/types.h: Add some additional checks to see
if clock_t or time_t is already defined.
