This fixes memory overflow caused by creating render result every time RenderResult is creating when updating sample and not being freed until tile is fully rendered. Solved in probably not best way -- RenderResult is being stored in RenderBuffers, so it's creating only once. This solves memory issues, but while was looking into this issue discovered dramatic slowdown caused by samples update in some files from mango svn. Solving this slowdown is becoming first priority from now on.