[babl] (11 commits) Non-fast-forward update to branch wip/pippin/inverted-cmyk

[Øyvind "pippin" Kolås <ok src gnome org>]

The branch 'wip/pippin/inverted-cmyk' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  80172b9... build: check for and link against lcms2
  1f529d1... babl: implement own reference code paths for CMYK color spa
  f995b12... extensions: replace naive-CMYK with new CMYK extensions
  68a28f8... babl: comment out unused model_is_rgba
  2c9783f... docs: update with information about CMYK
  061e635... fish-reference: add workaround for bizarre behavior that di
  f1147a1... babl-fish: print error message instead of blowing stack
  8422425... babl-space: improve initializiation of sRGB data in cmyk sp
  a32f389... docs: update

Commits added to the branch:

  10b4449... babl: avoid re-creating some existing conversions (*)
  c0a4a98... babl: properly cache runtime inserted conversions (*)
  d34171a... build: check for and link against lcms2
  078f37a... babl: implement own reference code paths for CMYK color spa
  7290c70... extensions: replace naive-CMYK with new CMYK extensions
  ed8bffd... babl: comment out unused model_is_rgba
  cdebeef... docs: update with information about CMYK
  c3b8cc8... fish-reference: add workaround for bizarre behavior that di
  658a12b... babl-fish: print error message instead of blowing stack
  691521f... babl-space: improve initializiation of sRGB data in cmyk sp
  b72af9a... docs: update

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