* exceptions.cc (pending_signals): Remove unneeded declaration.

* exceptions.cc (pending_signals): Remove unneeded declaration.
* sigproc.cc (pending_signals): Make static.
(wait_sig): Use defined values rather than integers for rc.  Never scan both
todo arrays as this could cause hangs if signals arrive from two different
sources.  Rename saw_pending_signals to saw_failed_interrupt.  Exit loop when
signal found.  Enter low-priority sleep, if necessary, after finished
signalling completion.  Set pending_signals when blocked
(from Pierre Humblet).