[Python-Dev] PEP 580 (C call protocol) minor update

I made some minor updates to PEP 580 (PEP editors: please merge https://github.com/python/peps/pull/741) and its reference implementation: - Added a new introductory section explaining the basic idea. - The C protocol no longer deals with __name__; a __name__ attribute is required but the protocol does not deal with its implementation. - The PEP no longer deals with profiling. This means that profiling only works for actual instances of builtin_function_or_method and method_descriptor. Profiling arbitrary callables would be nice, but that is deferred to a future PEP. The last two items are meant to simplify the PEP (although this is debatable since "simple" is very subjective). Enjoy! Jeroen.