* Added WikiPage to RequestContext and related so that it can be shared to avoid...

* Added WikiPage to RequestContext and related so that it can be shared to avoid creating a new object each time and thus avoiding database queries to load the state of the object
* Added Article::getPage() as accessor to the WikiPage object so that it can be set in the context from MediaWiki::initializeArticle()
* Use it WikiPage::main() to call doViewUpdates()

I'm doing to this now so that I can revert r105790 and use the WikiPage object before the 1.19 release