added gpu_mem runtime property
added gpu_mem runtime property

cbratschi/aminogfx-gl,joshmarinacci/aminogfx-gl,joshmarinacci/aminogfx-gl,cbratschi/aminogfx-gl,cbratschi/aminogfx-gl,cbratschi/aminogfx-gl,joshmarinacci/aminogfx-gl,joshmarinacci/aminogfx-gl,joshmarinacci/aminogfx-gl,cbratschi/aminogfx-gl