Fixed crash on self-referencing constant expression (part of a constant AST)
Merge branch 'PHP-5.6'

* PHP-5.6:
  Fixed crash on self-referencing constant expression (part of a constant AST)
Removed second zval_copy_ctor()
Merge branch 'PHP-5.6'

* PHP-5.6:
  Removed second zval_copy_ctor()