Log Message:
GIMP 2.8.20

Core:
 - Avoid D-Bus error message when built without D-Bus support
 - fix OS X min required conditional in gimpimagewindow.c
 - Saving to existing .xcf.bz and .xcf.gz files didn't truncate them
   and could lead to unnecessarily large files
 - Text layer created by gimp-text-fontname doesn't respect border
   when resized
 - avoid seeking when saving XCF files to prevent corruption with
   file network shares (fixed since 2014, but not mentioned in NEWS yet)

GUI:
 - Flow on Paint Dynamics editor dialog: the 'y' axis is indicating
   'Rate' instead 'Flow'
 - Vertical ruler shows artifacts if the status bar isn't showing
 - Tablet stylus misbehaves when crossing the edge of a dock in
   multi-window-mode
 - Disable the new "automatic window tabbing" feature introduced on macOS
   Sierra
 - Improve the visiblity of slider handles with dark themes
 - Make it harder to switch to renaming if selecting already selected
   items in resource lists

Tools:
 - make toggling to color picker mode of paint tools more robust

Libgimp:
 - call gimp_file_entry_set_filename() with filename encoding

Windows Installer:
 - Reduce the memory requirement when running the installer (has
   already been shipped in a 2.8.18 installer-only update)
 - Ship an updated libcairo to fix GTK+ UI rendering problems, like
   missing palette border/bevel and shadowa under tab labels

macOS DMG:
 - Ship the Tango icon theme with the DMG for a complete set of icons
 - fix the way mime data is copied into the bundle
 - no longer copy Pango modules into the bundle
 - prevent a crash caused by drag&drop on OSX by patching the included
   GTK+
 - ship a patch for gettext to make sure the preferred UI language
   will be used

Plug-ins:
 - Prevent the Python console from closing by the Escape key
 - Help browser does not launch on OS X
 - Filter 'Edge Detect/Difference of Gaussians' returns empty image
 - only use -xobjective-c for compile commands
 - mkgen.pl: fix calls to write_file() routine to write to current
   directory
 - When printing, the images are composed onto a white background to
   prevent printing a black box instead of a transaprent image
 - Fix color visison deficiency display filters to apply gamma
   correction directly