Most conflicts seemed to be simple enough. There were a lot of `append_text` to
`append` conversions for `Gtk::ComboBoxText`. The `PopUpCommon` class also saw
a lot of changes with non-trivial conflict resolutions.
resized, and display a tooltip.
The ICM tool has been reworked to avoid loosing space.
The curve's histogram are now displayed.
For Windows users, if you can't build the Gtk3 branch anymore with your
Gcc5.x compiler, try to uncomment line 20-21 of the main CMakeLists.txt.
For some reason, I had to comment that out.
