keyboard: Trivial update to code style

This fixed many code style issues in wm-common, and add
a few g_autofree when possible.

panels/keyboard/wm-common.h

@@ -1,5 +1,4 @@
-#ifndef WM_COMMON_H
-#define WM_COMMON_H
+#pragma once
 
 #define WM_COMMON_METACITY "Metacity"
 #define WM_COMMON_SAWFISH  "Sawfish"
@@ -7,11 +6,9 @@
 
 /* Returns a strv of keybinding names for the window manager;
  * using _GNOME_WM_KEYBINDINGS if available, _NET_WM_NAME otherwise. */
-GStrv wm_common_get_current_keybindings (void);
+GStrv      wm_common_get_current_keybindings           (void);
 
 gpointer   wm_common_register_window_manager_change   (GFunc    func,
-						       gpointer data);
+                                                       gpointer data);
+
 void       wm_common_unregister_window_manager_change (gpointer id);
-
-#endif /* WM_COMMON_H */
-