* 2.7:
[FrameworkBundle] Check for class existence before is_subclass_of
Update GroupSequence.php
Code enhancement and cleanup
[DI] Add anti-regression test
Revert "minor #19689 [DI] Cleanup array_key_exists (ro0NL)"
[BrowserKit] Fix cookie expiration on 32 bit systems
bumped Symfony version to 2.7.18
updated VERSION for 2.7.17
update CONTRIBUTORS for 2.7.17
updated CHANGELOG for 2.7.17
Update misleading comment about RFC4627