Fix #2916
CI_Encryption: Remove MCrypt 'work-arounds' for CAST-128 compatibility

Turns out it's OpenSSL's fault for performing 16 rounds instead of 12 for key sizes of 5-11 bytes.
Reference: http://tools.ietf.org/rfc/rfc2144.txt
Add support for simpler (Callable) hooks (issue #2917)
[ci skip] Fix a test skip message
Fix #2919
Add support for callable form validation rules
Fix #2928
Re-enable hhvm/mysqli tests
Fix #2928, #2929