* Introduce py_argparse_parse_plist!() to allow a more flexible
param list syntax.
* py_fn!() syntax changed
* Remove py_method!() / py_class_method!() macros.
These are of limited use when building dynamic types,
and not useful for py_class!() static types.
We now use the generic <DUMMY> hack to avoid duplicate extern "C" symbols.
See rust-lang/rust#26201.
py_module_initializer!() calls now need to manually concatenate the module
name with the prefixes "init" and "PyInit_".
