Shadow Files

- Re-enabled shadow files, but in a new, simpler manner, that allows the
  rc.shadow.command to override settings like color if necessary.
- Modifed A3 to capture program name and store it in the Context.

src/A3.cpp

@@ -211,6 +211,9 @@ void A3::categorize ()
           arg->_category = Arg::cat_command;
           found_command = true;
         }
+
+        // Context needs a copy.
+        context.program = arg->_raw;
       }
 
       // command