drm: msleep() must not sleep forever

* In some cases, the msleep() implementation called tsleep() with a
  timeout value of zero, making the calling thread sleep forever.

* Ensure tsleep() is always called with a minimal timeout value of
  one tick to avoid this situation.
tip(1): Raise WARNS to 2 and fix all corresponding warnings.

Also ansify, use -std=gnu99 like everywhere else and do some more
cleanups.
reboot - Mask SIGTERM to fix a self-immolation issue

* reboot is getting SIGTERM'd, possibly from its parent shell, before
  it can finish telling the system to reboot.  Mask this signal as well.

* But possibly exposed by earlier SMP work that could result in the
  signal getting in front of the final system call to reboot.

Submitted-by: YONETANI Tomokazu