Move booting to RubyXCompiler init

Also pass the source into the compile method.
This way compiler can be reused for subsequent compile.
Does remove some double boots, but no major time save

lib/risc.rb

@@ -17,6 +17,11 @@ end
 # of that subset that we need.
 # See risc/Readme
 module Risc
+  # module method to reset, and init
+  def self.boot!
+    Position.clear_positions
+    Builtin.boot_functions
+  end
 end
 
 require_relative "risc/padding"