Function unpack_bc5

engine/dlib/src/basis/encoder/basisu_gpu_texture.cpp:370–374

writes RG

	// writes RG
	void unpack_bc5(const void *pBlock_bits, color_rgba *pPixels)
	{
		unpack_bc4(pBlock_bits, &pPixels[0].r, sizeof(color_rgba));
		unpack_bc4((const uint8_t *)pBlock_bits + sizeof(bc4_block), &pPixels[0].g, sizeof(color_rgba));
	}

	// ATC isn't officially documented, so I'm assuming these references:
	// http://www.guildsoftware.com/papers/2012.Converting.DXTC.to.ATC.pdf