Make typed case-lambda methods work
Add more class/object functions to TR base-env
Fix static contract generation for method case->s
Fix DrRacket's insert-large-letters

This is a temporary fix in the sense that the typed/mred
wrapper that this relies on is incomplete. Once the typed
racket/gui bindings are merged, a more complete
insert-large-letters will be checked in.

Closes PR 14362