Fixing example.bro's auto-reST generation baseline test.

Adds a diff canonifier that skips diffing the places where example.bro
may use MutableVal derivatives (e.g. sets/tables), which don't always
generate the same ordering in the reST docs across runs.

testing/btest/Scripts/doc/example-diff-canonifier.py

@@ -0,0 +1,15 @@
+#!/usr/bin/python
+
+import sys
+import re
+
+# MutableVal derivatives (e.g. sets/tables) don't always generate the same
+# ordering in the reST documentation, so just don't bother diffing
+# the places where example.bro uses them.
+
+RE1 = "\d*/tcp"
+RE2 = "tcp port \d*"
+
+for line in sys.stdin.readlines():
+    if re.search(RE1, line) is None and re.search(RE2, line) is None:
+        print line