Skip test for decoding invalid numeric entities in 5.4+

I confirmed this is the same workaround that went into Drupal 8 via #2193023: EditorXssFilter/StandardTest::dataset #25 fails on php 5.4 so it looks good to go. (We can probably fix a couple minor things in the code comment on commit, "@fixme" => "@todo" and "its" => either "it's" or "it is".)

I'll mark #1210798: In PHP 5.4+, html_entity_decode() doesn't decode invalid numeric entities for Drupal 7 backport also.

Just uploading the real patch plus a no-op patch to double check that the test failures are what we expect them to be (given the confusing results above).

RTBC + 1, looks good to me.

Marking for commit.

Committed and pushed to 7.x, thanks!