Port __TRAIT__ and __CLASS__ to AST

Mostly finish class declarations (~50 failing tests)

Partial port of class declarations

Prepare zend_ast_decl for reuse with classes

Throw \self etc error

Could only enable this now that everything uses the new format

Fix class name resolution in traits

Improve class name handling

Port trait uses

Handle class const doc comment

Property doc comments not yet handled

Port class const decl

Port property declarations

Port methods

The duplicated magic method checks are ugly

Support static closures

Handle function doc comments

Fix lexer/compiler interdependency

Use dedicated func_decl ast node

Functions need a bunch of extra info, that becomes inconvenient
to handle using the normal ast structure.

Port closures

Port closure use

Port __METHOD__

Port __FUNCTION__ to AST

Preliminary function decl support

Problem: __FUNCTION__ etc don't work anymore, due to lexer/parser
interdependency.

Port parameter defs

Has one bug re \self

Rename params -> args

Port static vars

Need to figure out the constant expr stuff

Port try/catch

Down to 50 failing Zend tests