Minor tweaks to single-character command line option handling

- Use of "-B" now triggers usage output and errors out when Zeek
  wasn't built with debugging support.

- Always keep the perftools options (-m, -M) in the optparse string,
  for consistency with other flags dependent on configuration. We
  still fall through to usage and erroring out as before.

- Minor indentation fix.

src/Options.cc

@@ -350,13 +350,9 @@ Options parse_cmdline(int argc, char** argv)
 	};
 
 	char opts[256];
-	util::safe_strncpy(opts, "B:e:f:G:H:I:i:j::n:O:o:p:r:s:T:t:U:w:X:CDFNPQSWabdhuv",
+	util::safe_strncpy(opts, "B:e:f:G:H:I:i:j::n:O:o:p:r:s:T:t:U:w:X:CDFMNPQSWabdhmuv",
 	                         sizeof(opts));
 
-#ifdef USE_PERFTOOLS_DEBUG
-	strncat(opts, "mM", 2);
-#endif
-
 	int op;
 	int long_optsind;
 	opterr = 0;
@@ -444,9 +440,13 @@ Options parse_cmdline(int argc, char** argv)
 		case 'w':
 			rval.pcap_output_file = optarg;
 			break;
+
+#ifdef DEBUG
 		case 'B':
 			rval.debug_log_streams = optarg;
 			break;
+#endif
+
 		case 'C':
 			rval.ignore_checksums = true;
 			break;