python35: 3.5.8 -> 3.5.9

There were no new changes in version 3.5.9; 3.5.9 was released only because of a CDN caching problem,
which resulted in some users downloading a prerelease version of the 3.5.8 .xz source tarball.
Apart from the version number, 3.5.9 is identical to the proper 3.5.8 release.