Ensure a signalled process exits even if the GL driver hangs.

https://bugs.gentoo.org/478074

--- a/src/driver.c
+++ b/src/driver.c
@@ -397,6 +397,7 @@
 void signalHandler (int sig)
 {
 	signalled = 1;
+	alarm(3);	/* Self-destruct if something goes wrong */
 }
 
 int main (int argc, char *argv[])