Add back python2-setuptools

This adds back a python 2 version of setuptools but with all dependencies vendored
(the upstream default..). To allow users to install Python 2 packages we no longer
have in the repo etc which should help them transitioning.

This also adds conflicts between py2/3 setuptools because of the esy_install rename.

See #4993

mingw-w64-python2-setuptools/0005-execv-warning.patch

@@ -0,0 +1,14 @@
+--- setuptools-40.2.0/launcher.c.orig	2018-08-27 00:31:49.470981800 -0400
++++ setuptools-40.2.0/launcher.c	2018-08-27 00:35:03.568692800 -0400
+@@ -369,7 +372,11 @@ int run(int argc, char **argv, int is_gu
+ 
+     if (is_gui) {
+         /* Use exec, we don't need to wait for the GUI to finish */
++#ifdef __MINGW32__
++        _execv(ptr, (const char * const *)(newargs));
++#else
+         execv(ptr, (const char * const *)(newargs));
++#endif
+         return fail("Could not exec %s", ptr);   /* shouldn't get here! */
+     }
+