HHVM fixes - tests pass hunting [WIP]

One last assertion is not passing due to #162. Thinking about fix/workaround.

1st commit note: HHVM 3.3 [should be out](http://hhvm.com/blog/6083/hhvm-long-term-support) next Thursday.
This hack should not be needed anymore, since facebook/hhvm#1203 is fixed (currently only in master, but hopefully also in 3.3.0).