* Fix for r57997 and bug 21222: move math, gallery, pre and nowiki to a new module called CoreTagHooks, analogous to CoreParserFunctions.
* Extended the return interface for tag hooks in a way analogous to the one for parser functions, allowing <nowiki> and <html> to specify that they want to be in the nowiki replacement array instead of the general replacement array.
* Removed ParserOptions::setUseTeX() and related. If <math> is going to be registered in firstCallInit(), then it needs to be stable across multiple parser calls and not change based on parser options. Only one extension caller.
In parserTests.inc:
* Fixed parser test failures due to $wgMathDirectory not being properly set up. The math directory of the host wiki was being used, leading to a parser test failure if it was not writable.
* Fixed message cache hack from r15502. Made parser tests not fail in the case where a tested message is overwritten by the local wiki. All tests now pass on my installation.