Make overlaprenderer and materialpreload work with Qt 5.2

When building with Qt 5.2 or higher, a warning will be printed when
using the overlaprenderer, as the default batchrenderer should typically
be a better alternative. materialpreload will be relevant only
if the overlaprenderer is used.

Change-Id: I4899f8b4f45210c03fe08b1bb0940763683c99b3
Reviewed-by: Michael Brasser <michael.brasser@live.com>