Greetings,

OpenBSD/macppc does not complete early boot on mac99: OpenPIC can
reassert an interrupt still masked by CTPR; the edge triggered
decrementer does not raise on zero; successful CUDA ADB replies omit the
original command; and the fixed CUDA shift register delay can stretch
packet delivery past the guest timeout on hosts with coarse timers.

This series corrects these four behaviours and adds a functional test
which boots the official OpenBSD 7.9 macppc CD to the installer prompt.

P.S. this is second third to send the same patch because previous one
had missed maintainers.