[gtk] (13 commits) Non-fast-forward update to branch ngl-coloring-underlines

[Matthias Clasen <matthiasc src gnome org>]

The branch 'ngl-coloring-underlines' 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:

  f310260... gtk-demo: Make one text scroll benchmark harder
  308860d... ngl: Fix an oversight
  52f929e... ngl: Reserve a pixel in texture atlases
  de27150... ngl: Optimize underlines in text

Commits added to the branch:

  8b1fcb5... ngl: Use fp16 for colors (*)
  ae7f52d... ngl: Reduce vertex storage (*)
  7fe7b7a... ngl: Use a constant for (fp16)-1 (*)
  38c6fe2... Move color conversion up (*)
  9d81c12... Add an option to disable F16C (*)
  885a6b8... gsk: Add runtime checks for F16C (*)
  2d7169f... Work around compiler shortcomings on macOS (*)
  1c2238c... Merge branch 'font-fallback-fix' into 'master' (*)
  5d0a3bd... Merge branch 'half-float' into 'master' (*)
  e4a6101... gtk-demo: Make one text scroll benchmark harder
  e796394... ngl: Fix an oversight
  d8ba4b4... ngl: Reserve a pixel in texture atlases
  0caa28c... ngl: Optimize underlines in text

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