...only remembers horizontal radius, duplicates it for vertical
Keep a list of the GUI's chain buttons around. When changing the
entire config object like on reset or selecting saved settings, unlik
them all after remembering their "active" state, and after changing
the settings activate the ones that were active before, but only if
the values they link are still the same.
Allow propgui constructors to specify an (optional) callback function
when creating pickers, to be called when a color/coordinate is picked,
similarly to controller callbacks.
Implement picker callback support in GimpFilterTool. When the active
picker has an associated callback function, call it instead of the
class's color_picked() function.
Add lots of "#include <gegl.h>" to .c files that miss it, which is
now necessary, since this commit adds a Babl* parameter in
propgui-types.h.
