Fixes #1706: Thunder and lighting still occurs while the game is paused during the rain.

Can you make this enclose the "else" as well, like so:
<pre>
if (!paused)
{
   if (mCurrentWeather == "thunderstorm" && mNextWeather == "")
      ...
   else
       mRendering->getSkyManager()->setLightningStrength(0.f);
}
</pre>
As it is now, the lightning will be totally removed when paused, instead of just pausing its update.