Move builtin wholesale to Mom

Since Builtin generates risc, just like mom instructions, it was a design mistake to put builtin into risc in the first place. Now that borders are coming more into focus, it make much more sense to have the builtin in mom.
In fact the instructions should be moved out and a seperate invocation mechanism used , so functions can be parsed, not generated (wip)

test/vool/send/helper.rb

@@ -8,7 +8,7 @@ module Vool
 
     def setup
       Parfait.boot!(Parfait.default_test_options)
-      Risc::Builtin.boot_functions
+      Mom.boot!
       @compiler = compile_first_method( send_method )
       @ins = @compiler.mom_instructions.next
     end