removing builtin as a concept (wip)

the "old" way of generating compilers is now obsolete
we can use ruby code with mom macros to achieve the same
Three step wip
remove old builtin
fix tests (including adding necessary methods)
fixup and inclusion of builtin code to parfait

lib/mom/macro/exit.rb

@@ -1,14 +1,4 @@
 module Mom
-  module Builtin
-    class Exit < ::Mom::Instruction
-      def to_risc(compiler)
-        builder = compiler.builder(compiler.source)
-        builder.prepare_int_return # makes integer_tmp variable as return
-        Builtin.exit_sequence(builder)
-        return compiler
-      end
-    end
-  end
   class Exit < Macro
     def to_risc(compiler)
       builder = compiler.builder(compiler.source)