Change old-style function defintions to C89 prototypes.

Approved by releng.

Remove 3rd and 4th clause on Leo Weppelman's license. OK leo@.

merge ktrace-lwp.

__KERNEL_RCSID()

Don't set the PA_SER2 bit by default, this has the nasty side effect that
it disables the IDE hardware on the Falcon (Thanks Markus ;-) ). A function
is provided to toggle the bit.

Take out direct access to the YM2149. The chip definitions are moved
from video.h to ym2149reg.h.