Implement posix_errno

Summary: Closes https://github.com/facebook/hhvm/pull/3685

Reviewed By: @sgolemon

Differential Revision: D1541447
Add options parameter to DOMDocument::load/loadHTML()

Summary: Fixes #3695
Closes https://github.com/facebook/hhvm/pull/3696

Reviewed By: @sgolemon

Differential Revision: D1541940