Fix @dataProvider with PHPUnit 3.5.8+

Fix @dataProvider with PHPUnit 3.5.8+

MediaWikiTestCase duplicates code from PHPUnit constructor. It worked
fine until PHPUnit 3.5.8 made FrameWork_TestCase attributes private,
thus the children class is no more able to update them ($data for example)
The change break any tests making use of the @dataProvider helper.

PHPUnit commit:
https://github.com/sebastianbergmann/phpunit/commit/0b85d08c39ce689bc7320ebc03e7e5a4bfdbcbac

TESTS:
3.5.7  : OK -> OK
3.5.8  : KO -> OK
3.5.10 : KO -> OK

make databaseless
Tests: 486, Assertions: 73986, Incomplete: 1, Skipped: 3.

(skipped tests are SQLite related)