opal fix and minor

lib/register/parfait_adapter.rb

@@ -133,7 +133,7 @@ module Parfait
       string = ""
       index = 1
       while( index <= self.char_length)
-        string[index - 1] = get_char(index).chr
+        string += get_char(index).chr
         index = index + 1
       end
       string

test/compiler/statements/test_fields.rb

@@ -14,7 +14,7 @@ class Object
   end
 end
 HERE
-      @expect =  [Label, GetSlot, SetSlot, Label, FunctionReturn]
+      @expect =  [Label, GetSlot, GetSlot, GetSlot, SetSlot, Label, FunctionReturn]
       check
     end
 
@@ -60,8 +60,8 @@ class Object
   end
 end
 HERE
-      @expect =  [Label, GetSlot, SetSlot, GetSlot, GetSlot, SetSlot, Label ,
+      @expect =   [Label, RegisterTransfer, GetSlot, GetSlot, SetSlot, GetSlot, GetSlot ,
-                  FunctionReturn]
+               SetSlot, Label, FunctionReturn]
       check
     end
   end