Previously, this worked right if both AUTO_EOI_1 and AUTO_EOI_2 are
defined, but not if AUTO_EOI_1 is defined and AUTO_EOI_2 is not defined.
The latter case should be the default. DUMMY_NOPS should be the default
too. Currently there are only two NOPs slowing down rtcin() (although
there are no delays in writertc()) and several FASTER_NOPs slowing down
interrupt handling in vector.s.
Fix stack offsets for the (previously) unused untested
FAST_INTR_HANDLER_USES_ES case.