…parse()`

…r current code

Background: rope used to use `compile(..., ast.PyCF_ONLY_AST)` instead
of `ast.parse()`

rope code should not use standard library ast directly

`astutils` is a very bad module name for this, many parts of static
analysis can be described as "utilities to work with ast", so it's not
really descriptive enough as to what get_name_levels() and
`_NodeNameCollector` really does. The content of this current module
isn't actually generic utilities either, they do something very
specific, and so calling it `astutils` is also very misleading.