python/sepolgen: upgrade ply to release 3.11

PLY (Python Lex-Yacc) 3.11 has been released in February 2018:
- http://www.dabeaz.com/ply/index.html
- https://github.com/dabeaz/ply/releases/tag/3.11

Copy lex.py and yacc.py from this new release.

This fixes the following warning from "make test":

    python run-tests.py
    ../src/./sepolgen/lex.py:634: DeprecationWarning: Using or importing
    the ABCs from 'collections' instead of from 'collections.abc' is
    deprecated, and in 3.8 it will stop working
     if isinstance(t, collections.Callable):

(Python 3.3 moved collections.Callable to collections.abc.Callable)

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>