Fixes for Shinjiman's Special:Version updates r49995-r50121:

Fixes for Shinjiman's Special:Version updates r49995-r50121:
* Fixed formal parameter bloat in formatCredits() by passing the whole $extension array to the function and interpreting it there instead of in the caller.
* Fixed the overloading of getSvnRevision() with boolean parameters by splitting it into getSvnInfo(), which gets an associative array, and getSvnRevision(), which provides only the old behaviour as used by external callers like ApiQuerySiteinfo.
* A few tweaks and rewrites for other inelegant code