Per Nikerabbit's comment on r100621:

Per Nikerabbit's comment on r100621:
* Removed OutputPage::setPageTitleMsg() and OutputPage::setHTMLTitleMsg() and make OutputPage::setPageTitle() and OutputPage::setHTMLTitle() accept a Message object
* Updated core calls (including some that I missed last time because of non-matching case)
* Added Message::setContext() and use it in RequestContext so that I don't need to duplicate the call in OutputPage
* Yes, I'm calling $this->msg() on places and then setting the context one more time in OutputPage::setPageTitle() or OutputPage::setHTMLTitle(), but at least I won't be confused about which objects $