[cheese] (19 commits) ...Update NEWS for 3.9.3 release

[David King <davidk src gnome org>]

Summary of changes:

  ef21f49... Add a capsfilter to the video-source bin (*)
  1f0fe25... Remove extranous csp_post_balance element (*)
  f18ee5f... Fix no-video-after-switching-resolution problem (*)
  6f4127e... Improve error handling in CheeseCamera (*)
  cf493d7... Fix video-source memleak when switching cameras (*)
  e904325... Remove unused GstCameraBinFlags enum (*)
  79c8074... Fix cheese_camera_device_filter_caps warning (*)
  24d84d6... Fix cheese_camera_device_get_best_format memleak (*)
  8a8faca... Simplify returned GstCaps (*)
  8223201... Drop unused preview_caps variable (*)
  da9ad55... Only add videoconvert elements where necessary (*)
  daec944... Do not block the main valve while recording (*)
  606c262... Downscale image for effects-preview pipeline (*)
  6c5c7eb... Fix updating sensitivity of device selection combo (*)
  0cfc97b... Fix assertion failures when taking a photo (*)
  03ba5dc... Make the flash background white (*)
  ff4f591... Remove unused Cheese.MainWindow.get_data_file_dir
  039536f... Add documentation for CheeseCamera signals
  9733688... Update NEWS for 3.9.3 release

(*) This commit already existed in another branch; no separate mail sent