event mixer patch

[Charles D. <cd...@mv...>]

The attached patch creates a mixer device for the event interface, as
already exists for mice; indeed, it borrows (very) heavily from the
existing mousedev driver. create the device with "mknod events c 13
95". This patch also addresses an (unrelated) oops which turned up in
testing, though there's no promise that it fixes more than it induces.

Enjoy!