jpeg-turbo: add license details

- jpeg-turbo is covered by 3 licenses: IJG (libjpeg),
  BSD-3-Clause (TurboJPEG) and Zlib (SIMD)
- Add README.ijg
- Add hash for license files

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>