several larger changes came together, bit of cleaning too

- all code must be in functions (which must be in classes).
— changes a fair few tests
— also changes api, as method is not recursive, not passed around
- all state in instance vars in compiler (no accessors)
- class is another such variable, surely more coming
all green again

lib/register/assembler.rb

@@ -111,7 +111,7 @@ module Register
           begin
             code.assemble( stream )
           rescue => e
-            puts "Method error #{method.name}\n#{Sof.write(method.source.blocks).to_s[0...2000]}"
+            puts "Assembly error #{method.name}\n#{Sof.write(method.source.blocks).to_s[0...2000]}"
             puts Sof.write(code)
             raise e
           end