xrEngine: Stats: Separate FPS counter (Closes #171)

Слиты xottab-duty запросил слияние github/fork/vTurbine/0171_fps_counter в xd_dev

Created by: vTurbine

May disappear when:

  • Load screen is active (CApplication uses own draw loop while level is loading)
  • Level debug output is enabled (seems related to lost render target when bDebug is set)