[testing] Convert some "preparser" tests into "message".

test/message/message.status

Index: test/message/message.status
diff --git a/test/message/message.status b/test/message/message.status
index f764cd0a732823cb8bc5b683146af490ea609f97..cbfc687881abaeb7c3ec887c411a432af6aac455 100644
--- a/test/message/message.status
+++ b/test/message/message.status
@@ -29,6 +29,10 @@
 [ALWAYS, {
   # All tests in the bug directory are expected to fail.
   'bugs/*': [FAIL],
+  # We don't parse RegExps at scanning time, so we can't fail on octal
+  # escapes (we need to parse to distinguish octal escapes from valid
+  # back-references).
+  'strict-octal-regexp': [SKIP],
 }],  # ALWAYS
 ['ignition == True', {
   # TODO(4680): Some source positions are off with Ignition.