Enforce an upper limit on image size

[ajtribick]

It would probably make sense to impose a check on image sizes at load time to avoid trying to deal with huge images (or corrupt files whose metadata claims that the image dimensions are absurdly large). Any suggestions for an upper limit, e.g. maximum dimension 8192, 16384, 32768?

(For virtual textures this would be a per-tile limit)

[375gnu]

At least they should not be larger then max texture size.