Add support for callable form validation rules
Fix #2928
Re-enable hhvm/mysqli tests
Fix #2928, #2929
Check image path is include http:// or https://
Merge pull request #2934 from wuwx/patch-3

Check image path is include http:// or https://
Add support for protocol-relative URLs in HTML helpers img(), link_tag()
Partially revert PR #2190

The core shouldn't depend on constants that are not defined by itself