xbps-bin: use exit(2) rather than _exit(2).

This was causing premature exiting when piping the program!

--HG--
extra : convert_revision : xtraeme%40gmail.com-20091030004257-l94g3e88qroulfym

bin/xbps-bin/main.c

@@ -324,5 +324,5 @@ cleanup(int signum)
 	xbps_release_repolist_data();
 	xbps_release_regpkgdb_dict();
 	
-	_exit(signum);
+	exit(signum);
 }