[MINOR] halog: skip non-traffic logs for -st and -tc

Those were reporting stupid results in presence of administrative logs.
diff --git a/contrib/halog/halog.c b/contrib/halog/halog.c
index ebdcfcf..0162279 100644
--- a/contrib/halog/halog.c
+++ b/contrib/halog/halog.c
@@ -603,7 +603,16 @@
 		}
 
 		if (unlikely(filter & FILT_COUNT_STATUS)) {
-			b = field_start(line, STATUS_FIELD + skip_fields);
+			/* first, let's ensure that the line is a traffic line (beginning
+			 * with an IP address)
+			 */
+			b = field_start(line, SOURCE_FIELD + skip_fields);
+			if (*b < '0' || *b > '9') {
+				parse_err++;
+				continue;
+			}
+
+			b = field_start(b, STATUS_FIELD - SOURCE_FIELD + 1);
 			if (!*b) {
 				truncated_line(linenum, line);
 				continue;
@@ -616,7 +625,16 @@
 		}
 
 		if (unlikely(filter & FILT_COUNT_TERM_CODES)) {
-			b = field_start(line, TERM_CODES_FIELD + skip_fields);
+			/* first, let's ensure that the line is a traffic line (beginning
+			 * with an IP address)
+			 */
+			b = field_start(line, SOURCE_FIELD + skip_fields);
+			if (*b < '0' || *b > '9') {
+				parse_err++;
+				continue;
+			}
+
+			b = field_start(b, TERM_CODES_FIELD - SOURCE_FIELD + 1);
 			if (!*b) {
 				truncated_line(linenum, line);
 				continue;