reinstate the original (and dangerous) autopush in C
The regression for existing users was unnacceptable and
completely poor judgement on my part. This change brings
us back to potentially not-future-compatible code which
will impose maintenance burdens on us in the face of
future Ruby changes.
But TODAY, it is the most performant option for folks who
need to use autopush.
Revert "resurrect Kgio.autopush support in pure Ruby"
and "remove autopush support and make it a no-op"
This reverts commits
64dc570f4b99f68b5ed792b36e7e8abc3df74927
and
4347980fa66115425fa8b765353c8b1bfe5dec24.