strengthen more types in Data.Text

still need to prove the stronger types for `init` and `inits`
Data.Text.init checks again
bunch of updates to Data.Text.Lazy and strengthening of Data.Text.splitAt
add type for Lazy.replicate
fix up Lazy.pack
add hquals for Data.Text.Internal and Data.Text.Lazy.Internal

Lazy.splitAt types quite easily now, as do the mapAccums.

this requires a patch to fixpoint to use the fully-qualified names since Data.Text has a name conflict with Data.Text.Lazy