Also removed the callback functions for the existing regexes. Nothing
has to be or is encoded or escaped at this time, so preg_replace()
can be used instead of preg_replace_callback().
Change-Id: I8cdddd602dcf7b67b8f2b06149b6a0859c70342c
InstallDocFormatter didn't escape the double underscores in
__TOC__. I also noticed that wfEscapeWikiText had a similar
bug, which I reported as bug 53658 (fixed separately).
Change-Id: Ib5346b9c234f1c5ef361cc4357352b09def5dc25