Update for compatibility with the STT monad transformer

[jh3141]

trafficstars

Would be great if the hashtable implementations could be used with the STT transformer (https://hackage.haskell.org/package/STMonadTrans-0.3.3). Probably more usefully still would be to have an interface for parameterising how the state accesses are performed, assuming this can be written so that inlining avoids any performance penalty, so that they could be used with any monad that implements mutable state.

[ElvishJerricco]

Old issue, but figured I'd mention that Control.Monad.ST.Trans.Internal exports a function liftST :: Applicative m => ST s a -> STT s m a which does as much as you need.

[JasonSome]

@ElvishJerricco This function is hidden from exporting, and the issue still remains wide open.