osmo-nitb: be strict about cmdline args

Abort upon unknown options and missing option arguments. This came to my
attention while rewiring the -m and -M options: passing -M without argument
would launch nitb with wrong configuration. So, rather exit immediately.

If there are legacy options that should be ignored, they deserve an own 'case:'
in the option switch. There are none that I'm aware of though.

openbsc/src/osmo-nitb/bsc_hack.c

@@ -187,7 +187,9 @@ static void handle_options(int argc, char **argv)
 			rf_ctrl_path = optarg;
 			break;
 		default:
-			/* ignore */
+			/* catch unknown options *as well as* missing arguments. */
+			fprintf(stderr, "Error in command line options. Exiting.\n");
+			exit(-1);
 			break;
 		}
 	}