Some time RSN (hopefully no later than Sunday night), I will be
merging in some changes to increase the size of sigset_t, and the
maximum number of signals supported by the kernel.  There are several
side effects of this change:

1) The sigaction(2), sigprocmask(2), sigpending(2) and sigsuspend(2)
   ABIs will all change.  This requires the usually klugery.  Also,
   the latter 3 will now take `sigset_t *'s, rather than the previous
   special-case hacks.

2) I have to make a lot of changes to emulation code (sys/compat) to
   properly handle signal set conversion.  In particular, the way
   signal contexts are handled is really broken; I will be introducing
   a per-CPU, per-emulation version of sigreturn, and modifying the
   existing implementations of sendsig to use the correct signal
   context format for the emulation in question.

3) sigfillset(3) will become a system call -- because it only sets the
   bits corresponding to the supported signals.

Hopefully this won't cause too much pain.  B-)