* (bug 12294) Namespace class renamed to MWNamespace for PHP 5.3 compatibility

* (bug 12294) Namespace class renamed to MWNamespace for PHP 5.3 compatibility
* PHP 5.3 compatibility fix for wfRunHooks() called with no parameters

An autoloaded 'Namespace' class alias is retained for compatibility with
extensions which haven't updated to the new class name... however they too
will break on PHP 5.3. Yay!