o It switches kname to be just a pointer instead of an array
thus avoiding a couple of memcpy()s.
o It changes ioctl to unsigned from uint8_t.
o It changes the second keyhit limit to 3 seconds from 5
so that constant propagation can take place.
o It changes the ticks overflow computation as suggested by bde@.
o It removes bi_basemem/bi_extmem/bi_memsizes_valid setting from
bootinfo as it is unused.
Reviewed by: jhb
66f01f2e79