Fix x11-toolkits/py-kivy due to cython update.

Cython changes its temporary variable handling and now fails on the file:
  kivy/graphics/sahder/pyx

This has already been fixed upstream so just backport that fix.

Also, update the USE_PYTHON et al variables.

PR:		194065
Reported by:	John Marino (marino@FreeBSD.org)
Obtained from:	https://github.com/kivy/kivy/commit/b2bc566


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@369949 35697150-7ecd-e111-bb59-0022644237b5