Function to_6

external/basisu/transcoder/basisu_transcoder.cpp:14901–14901

	static inline uint8_t to_5(uint32_t v) { v = v * 31 + 128; return (uint8_t)((v + (v >> 8)) >> 8); }
	static inline uint8_t to_6(uint32_t v) { v = v * 63 + 128; return (uint8_t)((v + (v >> 8)) >> 8); }

	// Good references: squish library, stb_dxt.
	void encode_bc1(void* pDst, const uint8_t* pPixels, uint32_t flags)