Fixed kernel format checking:

Fixed kernel format checking:
- plain %r and %z were disallowed.  The hard NULs in the warnings were
  hopefully caused by disallowing of plain formats being nonsense.
- new formats for shortening to a byte were allowed, but even the libc
  printf doesn't support them.
- old %hr and %hz formats were allowed, but the kernel printf doesn't
  support them.  The kernel doesn't support %hd either, but this is
  harder to fix.

Submitted by:	bde