some helper functions

for when i started the assembler div10
in the end i did the div10 in some, so no need

lib/register/instructions/operator_instruction.rb

@@ -13,6 +13,9 @@ module Register
       "OperatorInstruction: #{left} #{operator} #{right}"
     end
 
+    def self.op source , operator , left , right
+      OperatorInstruction.new source , operator , left , right
+    end
   end
 
 end