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

Store (bad) estimate of lineno with ast

Currently not used yet

Port try/catch

Down to 50 failing Zend tests

Port switch

Port foreach

Port if (partial)

Support creating of ast nodes with >3 children

Port do/while

Port while

Note: From here on everything is broken

Port goto label

Make unticked_statement an ast node (usually NULL)

Port throw

Port echo

Port return statement

Rename ZEND_CONST to ZEND_AST_ZVAL

Bring static scalar AST more in line with normal AST

Const eval unary pm (as previously)

Implement constant expression folding as a separate pass

Support string interpolation

zend_ast_dynamic_ast returns new node

AST stage 2.4

Add ability to specify additional attr in AST