Tag Stackless release 3.8.1

Tag Stackless release 3.8.0

Stackless issue #252: recreate tag v3.7.9-slp

Move tag v3.7.9-slp from commit 8ad319a to commit 7613c31
to fix our online manual at https://stackless.readthedocs.io/en/v3.7.9-slp.

Stackless issue #252: recreate tag v3.6.13-slp

Move tag v3.6.13-slp from commit 8d0e9a0 to commit f7d6c5b.
to fix our online manual at https://stackless.readthedocs.io/en/v3.6.13-slp.

Tag Stackless release 3.7.8

Tag Stackless release 3.7.7

Tag Stackless release 3.7.6

tag v3.6.12-slp

tag v3.6.11-slp

tag v3.6.10-slp