OpenImageIO 2.2.9.0

Release 2.2.9 (1 Dec 2020) -- compared to 2.2.8

• TIFF: Fix reading files with "separate" planarconfig and rowsperstrip more
  than 1. #2757 (2.3.0.1/2.2.9)
• RAW: add "raw:user_flip" input configuration hint to control this option
  in the underlying libraw. #2769 (2.3.1.0)
• PNG: Read Exif data from PNG files. #2767
• BMP: Fix reading BMP images with bottom-to-top row order. #2776
• Work to ensure that OIIO will build correctly against the upcoming
  Imath 3.0 and OpenEXR 3.0.
• Make the OIIO CMake files work properly if OIIO is a subproject. Also
  various other CMake script refactoring. #2770