This hasn't been used for a very, very, very long time, (since before
OpenBSD had dri support, for example) and it causes segfaults on dri
drivers when sigio is disabled. Now we don't need to do context swaps on sigio
nor are we trying to do interrupts in userland (thank fuck for that) this
function can die the death that I intended it to die about two years ago, may it
burn.
The kernel support the the sigio ioctl will be removed in a couple of
weeks to give people time to update (right now it accepts it, then
ignores it).
ok kettenis@, matthieu@.
