- Always include the ie_disable and ie_eoi methods in 'struct intr_event'
  and collapse down to one intr_event_create() routine.  The disable and
  eoi hooks simply aren't used currently in the !INTR_FILTER case.
- Expand 'disab' to 'disable' in a few places.
- Use function casts for arm and i386:intr_eoi_src() instead of wrapper
  routines since to trim one extra indirection.

Compiled on:	{arm,amd64,i386,ia64,ppc,sparc64} x {FILTER, !FILTER}
Tested on:	{amd64,i386} x {FILTER, !FILTER}