Merge branch 'scalar_type_hints_v5'

* scalar_type_hints_v5: (65 commits)
  Fixed in-place modification of IS_CONST operand
  Changed SKIPIF messages
  ZPP changed to lazely check for "strict/weak" only if it's really necessary. Cleanup.
  cleanup
  Fixed return type hint handling for constants
  Fixed tests
  Imroved ZPP rules (condititins reoredered to prevent duplicate checks)
  Fixed comments
  Fixed error messages
  Improved type hinting:
  Fixed white spaces
  Add check for maintaining reference all the way through both type and return values
  Reduce the number of times that the zval needs to be separated in return type checking to those that are necessary
  Add test to ensure namespaced code can't use scalar types as class names
  Disallow relative namespace type declarations
  Add support and tests for null constant default values. Refactor complex conditionals into an extracted function for clarity and code-reuse
  Refactor as to not use call info, but add the flag to the op_array.
  Fix severity issues with callbacks, start work porting ZEND_STRLEN opcode to work with strict mode, more refactoring to come
  Fix C89 compatibility by moving a misplaced if statement
  Refactor gotos into more elaborate ifs to eliminate goto failure
  ...