[CMD] Improve the situations when the console title can be changed.

- Introduce two small helpers to change and restore the console title.
- Console title can change even when internal commands are executed.
- Note that when commands are run from within batch files, title is unchanged.
- When "cmd.exe /c command" is run, the console title is unchanged; however
  when "cmd.exe /k command" is run, the console title changes.

base/shell/cmd/title.c

@@ -28,7 +28,8 @@ INT cmd_title(LPTSTR param)
         return 0;
     }
 
-    bTitleSet = TRUE;
+    /* Set the new console title, and tell CMD to not reset it */
+    bTitleSet = FALSE;
     return ConSetTitle(param);
 }