(bug 35060) more allowed params to Special:MyPage, Special:MyTalk

(bug 35060) more allowed params to Special:MyPage, Special:MyTalk

I investigated the available parameters and considered which could be
plausibly useful for Special:MyPage and Special:MyTalk, and there are
quite a few. See inline documentation for a list of them. More could
potentially be added in the future if a use case is discovered.

This patch also make it possible for extensions to add their own
parameters to this list, through the new hook:
RedirectSpecialArticleRedirectParams

It has at least one application - with FlaggedRevs, it's desirable to
pass the "stable" flag through Special:MyPage. It also makes it simple
for individual servers that have some special reason to pass on a
particular parameter to do so in LocalSettings.php, simplifying
upgrades.

Change-Id: I3101fbe2eba8712b87a53706583f4e8f3e907478