Clean the manifest of old files

MANIFEST.in

@@ -1,6 +1,5 @@
 include setup.py
-recursive-include distutils.ext *.py *.c *.pem
-recursive-include python *.pyx *.pxd *.c *.h *.cfiles
+recursive-include python *.pyx *.pxd *.c *.h
 recursive-include src *.c *.h
 recursive-include doc/sphinx/source *.txt *.rst *.py
 recursive-include doc/sphinx/sphinxext *.py