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

Support directly calling closure

Fix previous commit

Introduce dereferencable_scalar to simplify future additions

Generalize static access syntax

Allow arrays + object access for new expressions

Integrate combined scalar as dereferencable

Generalize expression dereferencing

Minor cleanup

Cleanup old grammar rules

Reintroduce new expression dereferencing

Remove reference_variable indirection

Make function calls directly callable

Recursive definition for object proprety fetches

LTR static member access

Use recursion for property fetches

Get rid of base_variable_with_function_calls

Temporarily disable complex variables in new expressions

Change precedence of $ operator

$$foo['bar'] is now interpreted as ${$foo}['bar'] rather than
${$foo['bar']}.

Re-applyed Bob's patch with minor fixes

Reverted Bob's patch (it breaks many tests when run with opcache and needs to be fixed first).