Support the syntax for class member access on instantiation.

This adds support for syntax like (new Foo())->bar() as introduced
in PHP 5.4.

The bug, that ($a)-> still offers completion even though it is
invalid syntax (stupid PHP) remains though.

CCBUG: 305779
CCBUG: 297908
REVIEW: 115304
Add support for trait uses, as introduced in PHP 5.4

The error messages I used are as close as possible to the actual
errors given by PHP. We check for
- invalid function modifiers (static, final)
- property name conflicts between traits and main class
- method name conflicts between multiple traits

CCBUG: 305779
REVIEW: 115299