python-setuptools: Lots of fixes.

{cli,gui}{,-32,-64}.exe now handles /usr/bin/env ok and
looks in same dir as script for python executable.

Post installs are no longer needed.

This partially undoes Alexey's update to 7.0 which isn't
ready yet, AFAIK.

mingw-w64-python-setuptools/0001-mingw-python-fix.patch

@@ -0,0 +1,13 @@
+--- setuptools-5.4.1/setuptools/command/easy_install.py.orig	2014-02-11 21:11:57.898800000 +0400
++++ setuptools-5.4.1/setuptools/command/easy_install.py	2014-02-11 21:41:20.905000000 +0400
+@@ -1256,8 +1256,8 @@
+     )
+ 
+     DEFAULT_SCHEME = dict(
+-        install_dir='$base/Lib/site-packages',
+-        script_dir='$base/Scripts',
++        install_dir='$base/lib/python$py_version_short/site-packages',
++        script_dir='$base/bin',
+     )
+ 
+     def _expand(self, *attrs):