Message 258937 - Python tracker

I pushed an enhanced version of constant-3.patch:

* fix the compiler: don't emit LOAD_CONST for ast.Constant if the value is a string (str) or a number (int, float, complex), as done previously for ast.Str and ast.Num

* add unit tests on: the compiler (ensure that LOAD_CONST is emitted for constants), ast.get_docstring() and ast.literal_eval()