Some AMD drivers have a faulty GL_PROXY_TEXTURE_.. check.
This patch replaces the test of consistency and capacity made with GL_PROXY_TEXTURE_.. in the AMD driver with one that checks only if the texture fits within the size and layer limits.
I was unable to determine which cards have this defect, but since rB141e94f87ff2 fixes a similar problem and applies to all AMD GPUs, this patch also applies to all.