Including appropriate casts, and Num/Eq/Ord/Show implementations.
Also includes new primitives in Data.Buffer, and calls to foreign
functions in C as 'unsigned'.
Still a couple of things to resolve in coverage and totality checking
before we can switch on %default, so don't expect quite the right
behaviour just yet. More progress though!
Also working on this has caught a few totality errors in the Idris 2
code base that Idris 1 missed... so these are fixed on the way.
