Fixed a bug in initialization of some StaticPrintConfig derived classes.

Merged implementation of support for "Octoprint-Cancelobject" #972
thanks @supermerill

src/libslic3r/PrintConfig.cpp

@@ -930,6 +930,15 @@ void PrintConfigDef::init_fff_params()
     def->mode = comExpert;
     def->default_value = new ConfigOptionEnum<GCodeFlavor>(gcfRepRap);
 
+    def = this->add("gcode_label_objects", coBool);
+    def->label = "Label objects";
+    def->tooltip = "Enable this to add comments into the G-Code labeling print moves with what object they belong to,"
+                   " which is useful for the Octoprint CancelObject plugin. This settings is NOT compatible with "
+                   "Single Extruder Multi Material setup and Wipe into Object / Wipe into Infill.";
+    def->cli = "gcode-label-objects!";
+    def->mode = comAdvanced;
+    def->default_value = new ConfigOptionBool(0);
+
     def = this->add("high_current_on_filament_swap", coBool);
     def->label = L("High extruder current on filament swap");
     def->tooltip = L("It may be beneficial to increase the extruder motor current during the filament exchange"