gdk: Make gdk_keyval_name() return a const char

The string is const, so return it like that.

gdk/gdkkeys.c

@@ -738,7 +738,7 @@ gdk_keymap_get_modifier_mask (GdkKeymap         *keymap,
  *     of the key, or %NULL if @keyval is not a valid key. The string
  *     should not be modified.
  */
-gchar *
+const gchar *
 gdk_keyval_name (guint keyval)
 {
   return _gdk_keyval_name (keyval);

gdk/gdkkeys.h

@@ -133,7 +133,7 @@ GdkModifierType gdk_keymap_get_modifier_mask       (GdkKeymap           *keymap,
 /* Key values
  */
 GDK_AVAILABLE_IN_ALL
-gchar*   gdk_keyval_name         (guint        keyval) G_GNUC_CONST;
+const gchar*gdk_keyval_name      (guint        keyval) G_GNUC_CONST;
 
 GDK_AVAILABLE_IN_ALL
 guint    gdk_keyval_from_name    (const gchar *keyval_name);

gtk/a11y/gtkaccessibilityutil.c

@@ -131,7 +131,7 @@ atk_key_event_from_gdk_event_key (GdkEventKey       *key,
 
   event->state = state;
   event->keyval = keyval;
-  event->string = gdk_keyval_name (keyval);
+  event->string = (char *) gdk_keyval_name (keyval);
   event->length = strlen (event->string);
   event->keycode = keycode;
   event->timestamp = gdk_event_get_time ((GdkEvent *)key);

gtk/gtkaccelgroup.c

@@ -1418,10 +1418,10 @@ gtk_accelerator_get_label_with_keycode (GdkDisplay      *display,
  * so no need to be UTF-8 safe.
  */
 static void
-append_without_underscores (GString *s,
-                            gchar   *str)
+append_without_underscores (GString     *s,
+                            const gchar *str)
 {
-  gchar *p;
+  const gchar *p;
 
   if (g_str_has_prefix (str, "XF86"))
     p = str + 4;
@@ -1722,7 +1722,7 @@ gtk_accelerator_print_label (GString        *gstring,
     }
   else if (!append_keyval_symbol (accelerator_key, gstring))
     {
-      gchar *tmp;
+      const gchar *tmp;
 
       tmp = gdk_keyval_name (gdk_keyval_to_lower (accelerator_key));
       if (tmp != NULL)

gtk/gtkshortcutlabel.c

@@ -129,7 +129,7 @@ get_labels (guint key, GdkModifierType modifier, guint *n_mods)
   const gchar *labels[16];
   GList *freeme = NULL;
   gchar key_label[6];
-  gchar *tmp;
+  const gchar *tmp;
   gunichar ch;
   gint i = 0;
   gchar **retval;