Bring yarn up to date.
Factor repetition and make builtin calls explicit.
Remember to yarn the prelude.
WIP
Add Makefile rule to build interpreter.
WIP Moving to shared_ptr from union.
WIP
WIP Add 'execute' stubs.
WIP adding builtins; inflooping, possibly due to 'if'.
WIP Crap
WIP Beer works. Failure at __char_to_int in tictactoe.ktn.