interrupt handlers into intrtab[] array, rather than the idea of devices
in 'psuedo' TURBOchannel slots.
- Nuke symbols for psuedo TC slots.
- Abandon never/unlikely used intr_disestablish()s.
- Rework ibus device configuration and interrupt handler assignment.
- Remove TC device exposure in 'mainbus.c'
- Squash 'ibus_{3100,5100}.c' into a file; it can not cope with 3max.
- 'struct confargs' -> 'struct mainbus_attach_args'
Now about to remove tc_slot_info[] and tc_enable_interrupt inherited from
4.4BSD.
nisimura