* gnome: use const pointers where applicable

gnome/src/conference_obj.c

@@ -150,7 +150,7 @@ void conference_participant_list_update(gchar** participants, conference_obj_t*
     }
 
     for (gchar **part = participants; part && *part; ++part) {
-        gchar *call_id = (gchar *) (*part);
+        const gchar *call_id = (const gchar *) (*part);
         callable_obj_t *call = calllist_get_call(current_calls_tab, call_id);
 
         if (call->_confID != NULL) {

gnome/src/contacts/calltree.c

@@ -955,7 +955,7 @@ void calltree_add_conference_to_current_calls(conference_obj_t* conf)
         DEBUG("Calltree: Determine if at least one participant uses SRTP");
 
         for (GSList *part = conf->participant_list; part; part = g_slist_next(part)) {
-            const gchar * const call_id = (gchar *) part->data;
+            const gchar * const call_id = (const gchar *) part->data;
             callable_obj_t *call = calllist_get_call(current_calls_tab, call_id);
 
             if (call == NULL)

gnome/src/dbus/dbus.c

@@ -1722,7 +1722,7 @@ gchar **
 dbus_get_participant_list(const gchar *confID)
 {
     GError *error = NULL;
-    char **list = NULL;
+    gchar **list = NULL;
 
     DEBUG("DBUS: Get conference %s participant list", confID);
     org_sflphone_SFLphone_CallManager_get_participant_list(call_proxy, confID, &list, &error);