* sigproc.cc (no_signals_available): Return true if sending to self from the

* sigproc.cc (no_signals_available): Return true if sending to self from the
signal thread.
(wait_sig): Correct so that WaitForSingleObject is called when hMainThread is
!= 0, rather than the reverse.
* cygheap.cc (cygheap_fixup_in_child): Clarify potential error message.
* fork.cc (fork_copy): Cosmetic change.