- Don't do longjmp()s from inside a signal handler. Even though I got
things to work the way I wanted, it's bad karma.
- Remember to clear the sa_mask with sigemptyset() before masking signals
when using sigaction() to set up the SIGIO handler.
- Break out of the wait loop in yppush_exit() when the five minute
timeout expires instead of looping around for another pass. If ypxfr
on the other end fails somehow and never sends a response, we don't
want to wait around forever.