Nondeterministic results in ASTC w/ varying partitions

[Jbudone]

Running CompressBlocksASTC for a single 1024x1024 image under ASTC8x8 produces different results than combining 8 iterations of CompressBlocksASTC for 1024x128 portions of the same image:

Attempt 1: result = CompressBlocksASTC for 1024x1024 image (ASTC8x8)

Attempt 2: result0 = CompressBlocksASTC for 1024x128 image (offset = 0) (ASTC8x8) result1 = CompressBlocksASTC for 1024x128 image (offset = 128) (ASTC8x8) result2 = CompressBlocksASTC for 1024x128 image (offset = 256) (ASTC8x8) result3 = CompressBlocksASTC for 1024x128 image (offset = 384) (ASTC8x8) result4 = CompressBlocksASTC for 1024x128 image (offset = 512) (ASTC8x8) result5 = CompressBlocksASTC for 1024x128 image (offset = 640) (ASTC8x8) result6 = CompressBlocksASTC for 1024x128 image (offset = 768) (ASTC8x8) result7 = CompressBlocksASTC for 1024x128 image (offset = 896) (ASTC8x8) result = { result0, result1, result2, .... }