chg: reset signal handlers to default before waiting pager
Our signal handlers forward signals to the server process, but it will
disappear soon after hgc_close(). So we should unregister handlers before
hgc_close(). Otherwise chg would abort due to kill(perrpid, sig) failure.
The problem is spotted by SIGWINCH while waiting pager termination.
copyright (c) 2006-2010 David JEAN LOUIS
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