Fix linking against boost
Fix linking against boost

Building against recent enough boost requires to explicitly link against
boost_system. (Observed with boost 1.50)

Add the missing library to cmake rules.

AlphaStaxLLC/tundra,AlphaStaxLLC/tundra,AlphaStaxLLC/tundra,realXtend/tundra,jesterKing/naali,pharos3d/tundra,pharos3d/tundra,BogusCurry/tundra,realXtend/tundra,jesterKing/naali,AlphaStaxLLC/tundra,jesterKing/naali,pharos3d/tundra,AlphaStaxLLC/tundra,realXtend/tundra,jesterKing/naali,BogusCurry/tundra,pharos3d/tundra,AlphaStaxLLC/tundra,pharos3d/tundra,jesterKing/naali,BogusCurry/tundra,BogusCurry/tundra,BogusCurry/tundra,realXtend/tundra,BogusCurry/tundra,pharos3d/tundra,realXtend/tundra,realXtend/tundra,jesterKing/naali,jesterKing/naali