No longer demand black leaves in Dict.{get,map,foldl,foldr}
No longer demand black leaves in Dict.{get,map,foldl,foldr}

The color of leaves is an invariant that needs to be maintained by
Dict.update. It is not the responsibility of other functions to check
this invariant at runtime. Invariant checks should be in tests.

This also gets rid of some “missing pattern” errors that need to get
resolved.

rgrempel/core,rgrempel/core,ThomasWeiser/core,bradurani/core,bradurani/core,Pisys/core,alexiamcdonald/elm-core,simonh1000/core,ThomasWeiser/core,simonh1000/core,alexiamcdonald/elm-core,martinos/core,Pisys/core,martinos/core