Some refactoring of fn/const resolution

Drop addition of weird \ prefix for FQ consts

Also fixes a resolution bug

Rename ZEND_CONST to ZEND_AST_ZVAL

Remove obseleted grammar productions

Reuse expr for static_scalar

Handle ::class in const expr via ast as well

Compile const refs to CONST

Compile class const refs to CONST zval

Remove static_scalar_base

Handle trait __CLASS__ in parser

Bring static scalar arrays in line

Bring static scalar AST more in line with normal AST

Const eval unary pm (as previously)

Move T_STRING_VARNAME handling

Support string interpolation

zend_ast_dynamic_ast returns new node

AST stage 2.4

Support yield without parens

for now => is lowest-prec right-assoc

AST stage 1.9

Expressions (mostly) use the AST

AST-based compiler: Stage 1

Accept static member fetch in new variable (BC)

Allow only simple variables with global keyword

Merge and rename to member_name

Remove duplication

Forbid writing to temporary expressions