[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:

  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

Commits added to the branch:

  a5f169b... tests: make srgb-to-lab-u8 also compile stand-alone (*)
  de0fc82... build: check for and link against lcms2
  8de9fcf... babl: implement own reference code paths for CMYK color spa
  0b489b1... extensions: replace naive-CMYK with new CMYK extensions
  64c6a41... babl: comment out unused model_is_rgba
  5d68fe2... docs: update with information about CMYK
  117f067... fish-reference: add workaround for bizarre behavior that di
  b67ea2e... babl-fish: print error message instead of blowing stack
  5a23818... babl-space: improve initializiation of sRGB data in cmyk sp
  d06f905... docs: update
  aaf3184... babl: hold mutex during reference conversions

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