Attempt to prevent progmode capture from hanging on program death.

I was attempting to read back any last words the program might have
uttered, but if it said nothing, we would hang. I would not have
expected this behavior from a pipe (actually, socketpair) when the
other end has gone away! But, make it non blocking before we read
to be safe.

clientside/os/capture/capture.c

@@ -1765,6 +1765,7 @@ progmode(int isrestart)
 			warning("%s: program (pid=%d) died immediately, "
 				"status=0x%x, output:",
 				Devname, progpid, status);
+			fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 			cc = read(pipefds[0], buf, sizeof(buf)-1);
 			if (cc > 0) {
 				buf[cc] = '\0';