ffmpegthumbnailer: Update to 2.2.2

FFmpegThumbnailer 2.2.2
- Removed unstable continuous thumbnail creation

FFmpegThumbnailer 2.2.1
- CMake improvements: required CMake version is now 3.5 or newer
- Fix anamorphic height (thanks to cmrd-senya)
- Fix libffmpegthumbnailer.pc to work with multilib systems (thanks to orbea)
- Fix rotation of 180属 rotated videos (thanks to munzli)
- Fix prefer_embedded_metadata in c api (thanks to aedis)
- Fix crash when setting a log callback using the c api
- Check for https as well when skipping stat call (thanks to HearstCorp)
- Support specifying the size as string using the c api
- Support raw rgb data as image type
- Print warnings on stderr instead of stdout
- Support for continuous thumbnail creation

(nia)