app: GtkAction -> GAction madness part two

Change all action callbacks so they can be invoked by a GAction:

- add GimpActionCallback typedef:
  void (* cb) (GimpAction*, GVariant*, gpointer)
- change all action callbacks to the GimpActionCallback signature
- add "gimp-activate" and "gimp-change-state" signals to GimpAction,
  with the same signature as the resp. GAction signals
- remove all other custom action signals and only use the new
  GimpAction signals
- pass around appropriate GVariants containing booleans, int32,
  strings
- badly hack around to force a GimpProcedure pointer into a
  uint64 variant
- remove all G_CALLBACK() casts from all action callbacks,
  they all have the same signature now

(cherry picked from commit 3b6b3fc189)

app/actions/select-actions.c

@@ -49,92 +49,92 @@ static const GimpActionEntry select_actions[] =
   { "select-all", GIMP_ICON_SELECTION_ALL,
     NC_("select-action", "_All"), "<primary>A",
     NC_("select-action", "Select everything"),
-    G_CALLBACK (select_all_cmd_callback),
+    select_all_cmd_callback,
     GIMP_HELP_SELECTION_ALL },
 
   { "select-none", GIMP_ICON_SELECTION_NONE,
     NC_("select-action", "_None"), "<primary><shift>A",
     NC_("select-action", "Dismiss the selection"),
-    G_CALLBACK (select_none_cmd_callback),
+    select_none_cmd_callback,
     GIMP_HELP_SELECTION_NONE },
 
   { "select-invert", GIMP_ICON_INVERT,
     NC_("select-action", "_Invert"), "<primary>I",
     NC_("select-action", "Invert the selection"),
-    G_CALLBACK (select_invert_cmd_callback),
+    select_invert_cmd_callback,
     GIMP_HELP_SELECTION_INVERT },
 
   { "select-float", GIMP_ICON_LAYER_FLOATING_SELECTION,
     NC_("select-action", "_Float"), "<primary><shift>L",
     NC_("select-action", "Create a floating selection"),
-    G_CALLBACK (select_float_cmd_callback),
+    select_float_cmd_callback,
     GIMP_HELP_SELECTION_FLOAT },
 
   { "select-feather", NULL,
     NC_("select-action", "Fea_ther..."), NULL,
     NC_("select-action",
         "Blur the selection border so that it fades out smoothly"),
-    G_CALLBACK (select_feather_cmd_callback),
+    select_feather_cmd_callback,
     GIMP_HELP_SELECTION_FEATHER },
 
   { "select-sharpen", NULL,
     NC_("select-action", "_Sharpen"), NULL,
     NC_("select-action", "Remove fuzziness from the selection"),
-    G_CALLBACK (select_sharpen_cmd_callback),
+    select_sharpen_cmd_callback,
     GIMP_HELP_SELECTION_SHARPEN },
 
   { "select-shrink", GIMP_ICON_SELECTION_SHRINK,
     NC_("select-action", "S_hrink..."), NULL,
     NC_("select-action", "Contract the selection"),
-    G_CALLBACK (select_shrink_cmd_callback),
+    select_shrink_cmd_callback,
     GIMP_HELP_SELECTION_SHRINK },
 
   { "select-grow", GIMP_ICON_SELECTION_GROW,
     NC_("select-action", "_Grow..."), NULL,
     NC_("select-action", "Enlarge the selection"),
-    G_CALLBACK (select_grow_cmd_callback),
+    select_grow_cmd_callback,
     GIMP_HELP_SELECTION_GROW },
 
   { "select-border", GIMP_ICON_SELECTION_BORDER,
     NC_("select-action", "Bo_rder..."), NULL,
     NC_("select-action", "Replace the selection by its border"),
-    G_CALLBACK (select_border_cmd_callback),
+    select_border_cmd_callback,
     GIMP_HELP_SELECTION_BORDER },
 
   { "select-flood", NULL,
     NC_("select-action", "Re_move Holes"), NULL,
     NC_("select-action", "Remove holes from the selection"),
-    G_CALLBACK (select_flood_cmd_callback),
+    select_flood_cmd_callback,
     GIMP_HELP_SELECTION_FLOOD },
 
   { "select-save", GIMP_ICON_SELECTION_TO_CHANNEL,
     NC_("select-action", "Save to _Channel"), NULL,
     NC_("select-action", "Save the selection to a channel"),
-    G_CALLBACK (select_save_cmd_callback),
+    select_save_cmd_callback,
     GIMP_HELP_SELECTION_TO_CHANNEL },
 
   { "select-fill", GIMP_ICON_TOOL_BUCKET_FILL,
     NC_("select-action", "_Fill Selection Outline..."), NULL,
     NC_("select-action", "Fill the selection outline"),
-    G_CALLBACK (select_fill_cmd_callback),
+    select_fill_cmd_callback,
     GIMP_HELP_SELECTION_FILL },
 
   { "select-fill-last-values", GIMP_ICON_TOOL_BUCKET_FILL,
     NC_("select-action", "_Fill Selection Outline"), NULL,
     NC_("select-action", "Fill the selection outline with last used values"),
-    G_CALLBACK (select_fill_last_vals_cmd_callback),
+    select_fill_last_vals_cmd_callback,
     GIMP_HELP_SELECTION_FILL },
 
   { "select-stroke", GIMP_ICON_SELECTION_STROKE,
     NC_("select-action", "_Stroke Selection..."), NULL,
     NC_("select-action", "Paint along the selection outline"),
-    G_CALLBACK (select_stroke_cmd_callback),
+    select_stroke_cmd_callback,
     GIMP_HELP_SELECTION_STROKE },
 
   { "select-stroke-last-values", GIMP_ICON_SELECTION_STROKE,
     NC_("select-action", "_Stroke Selection"), NULL,
     NC_("select-action", "Stroke the selection with last used values"),
-    G_CALLBACK (select_stroke_last_vals_cmd_callback),
+    select_stroke_last_vals_cmd_callback,
     GIMP_HELP_SELECTION_STROKE }
 };