rename data_object to string_node and move the padding there

lib/asm/arm/arm_assembler.rb

@@ -6,7 +6,7 @@ require 'asm/arm/generator_label'
 require 'asm/nodes'
 require 'stream_reader'
 require 'stringio'
-require "asm/data_object"
+require "asm/string_node"
 
 module Asm
   module Arm

lib/asm/arm/normal_builder.rb

@@ -46,7 +46,7 @@ module Asm
       def build_operand(arg , position = 0) 
         #position only needed for calculating relative addresses to data objects
         #there is a design stink here which makes my head ache. But shanti shanti
-        if arg.is_a?(Asm::DataObject)
+        if arg.is_a?(Asm::StringNode)
           # do pc relative addressing with the difference to the instuction
           # 8 is for the funny pipeline adjustment (ie oc pointing to fetch and not execute)
           arg = Asm::NumLiteralNode.new( arg.position - position - 8 )