Fix AbstractTexture::setWrapping() for rectangle textures.
Fix AbstractTexture::setWrapping() for rectangle textures.

Sampler::Wrapping::ClampToBorder was mistakenly disallowed. All the
tests are now passing again.

ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,DerThorsten/magnum,ashimidashajia/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,ashimidashajia/magnum