Fix bugs in ETC2 and ETC2_PUNCHTHROUGH processing

Fix a bug in ETC2 block decompression (planar mode) and bugs in
ETC2_PUNCHTHROUGH decompression (non-opaque differential mode).

Signed-off-by: Harm Hanemaaijer <[email protected]>

Bump version to v0.1.2

Signed-off-by: Harm Hanemaaijer <[email protected]>

Bump version to 0.1.1

Signed-off-by: Harm Hanemaaijer <[email protected]>

Update README

Signed-off-by: Harm Hanemaaijer <[email protected]>

Eliminate compilation warning messages

Signed-off-by: Harm Hanemaaijer <[email protected]>

Speed-up integer division using look-up tables

Speed up division by 3, 5, or 7 as used by BC1/2/3 and RGTC1/2 (BC4/5)
decompression using look-up tables.

Signed-off-by: Harm Hanemaaijer <[email protected]>

Add SetMode functions for ETC2_EAC, BPTC and BPTC_FLOAT

Signed-off-by: Harm Hanemaaijer <[email protected]>

Add README file with detailed instructions, update README.md

Signed-off-by: Harm Hanemaaijer <[email protected]>

Update README.md

Signed-off-by: Harm Hanemaaijer <[email protected]>

Update README.md

Signed-off-by: Harm Hanemaaijer <[email protected]>