This caused bug 16108, and also broke the patch to bug 3276. The commit
doesn't explain why it's useful or what it fixes, although Platonides
asked on Code Review in 2008, so that's two problems it's caused with no
benefits I've seen.
* Refactored Tidy function in a new class, MWTidy
* Only added Parser::tidy() for b/c, Parser::internalTidy() and Parser::externalTidy() were marked as private and are unused in core and extensions
* Added RELEASE-NOTES entry