[gnome-panel] panel-action-button: fix build warnings

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 2280f8b92a0b9b69528bce6a63b3c4810c202a15
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Sep 27 00:49:57 2015 +0300

    panel-action-button: fix build warnings

 gnome-panel/panel-action-button.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/gnome-panel/panel-action-button.c b/gnome-panel/panel-action-button.c
index 3863ef1..7e28936 100644
--- a/gnome-panel/panel-action-button.c
+++ b/gnome-panel/panel-action-button.c
@@ -376,10 +376,10 @@ panel_action_connect_server (GtkWidget *widget)
 
 typedef struct {
        PanelActionButtonType   type;
-       char                   *icon_name;
-       char                   *text;
-       char                   *tooltip;
-       char                   *drag_id;
+       const gchar            *icon_name;
+       const gchar            *text;
+       const gchar            *tooltip;
+       const gchar            *drag_id;
        void                  (*invoke)      (GtkWidget         *widget);
        void                  (*setup_menu)  (PanelActionButton *button);
        void                  (*invoke_menu) (PanelActionButton *button,
@@ -905,7 +905,7 @@ panel_action_button_set_dnd_enabled (PanelActionButton *button,
 
        if (enabled) {
                static GtkTargetEntry dnd_targets [] = {
-                       { "application/x-panel-applet-internal", 0, 0 }
+                       { (gchar *) "application/x-panel-applet-internal", 0, 0 }
                };
 
                gtk_widget_set_has_window (GTK_WIDGET (button), TRUE);