[gimp] (3 commits) Non-fast-forward update to branch wip/xcf-delta-compression

[N/A <ell src gnome org>]

The branch 'wip/xcf-delta-compression' 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:

  17a46d5... app: add delta-encoded zlib compression mode for XCF tiles
  7d430b7... devel-docs: document the new compression mode in xcf.txt
  911e232... app: add GIMP_TESTING_NO_DELTA_COMPRESSION environment flag

Commits added to the branch:

  7537cea... app: add delta-encoded zlib compression mode for XCF tiles
  f921180... devel-docs: document the new compression mode in xcf.txt
  cd5d382... app: add GIMP_TESTING_NO_DELTA_COMPRESSION environment flag