Tweaks to stop following warnings with PHP's E_STRICT error_reporting mode enabled:

Tweaks to stop following warnings with PHP's E_STRICT error_reporting mode enabled:
* Strict Standards: Non-static method DBLockForm::notWritable() should not be called statically in includes/SpecialLockdb.php on line 22
* Strict Standards: simplexml_load_file() [<a href='function.simplexml-load-file'>function.simplexml-load-file</a>]: /var/www/hosts/mediawiki/wiki/.svn/entries:3: parser warning : xmlns: svn: not a valid URI in includes/SpecialVersion.php on line 297
* Strict Standards: simplexml_load_file() [<a href='function.simplexml-load-file'>function.simplexml-load-file</a>]:    xmlns=&quot;svn:&quot;&gt; in includes/SpecialVersion.php on line 297
* Strict Standards: simplexml_load_file() [<a href='function.simplexml-load-file'>function.simplexml-load-file</a>]:                ^ in includes/SpecialVersion.php on line 297
* Strict Standards: Undefined index:  version in includes/SpecialVersion.php on line 122
* Strict Standards: Undefined index:  url in includes/SpecialVersion.php on line 124
* Strict Standards: Undefined index:  author in includes/SpecialVersion.php on line 123
* Strict Standards: Undefined index:  description in includes/SpecialVersion.php on line 125
* Strict Standards: Undefined index:  variable in includes/SpecialVersion.php on line 113
* Strict Standards: Undefined index:  other in includes/SpecialVersion.php on line 113