[issue19573] Fix the docstring of inspect.Parameter and the implementation of _ParameterKind

[Yury Selivanov]

Changes by Yury Selivanov <yselivanov.ml at gmail.com>:


----------
nosy: +yselivanov
versions: +Python 3.5 -Python 3.4

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19573>
_______________________________________