support binding gpointer (transfer none)
Submitted by Colin Walters
Link to original bug (#694770)
Description
This came up in an earlier bug that I'd link to if bugzilla search didn't suck, but basically it'd be nice for library authors to be able to return gpointer "keys" and be able to accept them in other APIs.
We could enable this if they were explicitly annotated as (transfer none) possibly.