* pinfo.h (EXITCODE_SET): Move out of range of Windows error.

* pinfo.h (EXITCODE_SET): Move out of range of Windows error.
(EXITCODE_NOSET): Ditto.
* sigproc.cc (no_signals_available): Remove check for hwait_sig.  Just rely on
my_sendsig.  Pass in an argument controlling when it is appropriate to test
EXITCODE_SET.
(proc_can_be_signalled): Remove checks for myself since this function is never
called in that context.
(sigproc_init): Pre-initialize my_sendsig to non-zero so that
proc_can_be_signalled will know that we expect to be signalable soon.
(sig_send): Change debugging output.