app, libgimp: replace GTK_STOCK_FOO by icon names

unless it's a stock ID used for an action button, will address that
later.

modules/color-selector-cmyk.c

@@ -117,7 +117,7 @@ colorsel_cmyk_class_init (ColorselCmykClass *klass)
 
   selector_class->name       = _("CMYK");
   selector_class->help_id    = "gimp-colorselector-cmyk";
-  selector_class->icon_name  = GTK_STOCK_PRINT;  /* FIXME */
+  selector_class->icon_name  = "document-print";  /* FIXME */
   selector_class->set_color  = colorsel_cmyk_set_color;
   selector_class->set_config = colorsel_cmyk_set_config;
 }