Strip local paths and copy hphp.tab.cpp to hphp/compiler/parser
Allow traits to implement interfaces

Add runtime support for implementing interfaces from traits.

e.g. if a class C uses a trait T that implements an interface I, then C is a subtype of I.

Reviewed By: @paroski

Differential Revision: D969512
Support arbitrary expressions inside empty()

PHP 5.5 now supports arbitrary expressions inside the empty() construct. We want to match Zend's behaviour.

For the newly supported cases, empty(E) is equivalent to !(E).

Reviewed By: @paroski

Differential Revision: D966136