[gtk] (4 commits) Non-fast-forward update to branch wip/smcv/reftest-tolerance

[Simon McVittie <smcv src gnome org>]

The branch 'wip/smcv/reftest-tolerance' 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:

  e75a3bc... reftest-compare: Fix spelling of "diff"
  5e1e9d6... reftests: Share reftest-compare.[ch] between GSK and GTK te
  8327746... reftest_compare_surfaces: Report how much the images differ
  6b73dcf... reftests: Allow ignoring individual tests or accepting mino

Commits added to the branch:

  b4a713e... reftest-compare: Fix spelling of "diff"
  9448e97... reftests: Share reftest-compare.[ch] between GSK and GTK te
  7249080... reftest_compare_surfaces: Report how much the images differ
  5ab3ef0... reftests: Allow minor differences to be tolerated