- SMPng lock the DRM. This is only partial -- there are a few code paths

- SMPng lock the DRM. This is only partial -- there are a few code paths
    used by root (the X Server) which are not locked. However, it should
    deal with lost-IRQ issues on -current which I think people have been
    experiencing but I am unable to reproduce (though I understand why they
    would occur, because of a bug of mine). Note that most of the locking
    (DRM_LOCK()/UNLOCK()) is all covered by Giant still, so it doesn't
    matter yet.
- Remove locking on FreeBSD-stable and NetBSD. These are covered by the
    fact that there is no reentrancy of the kernel except by interrupts,
    which are locked using spldrm()/splx() instead.