[retro-gtk] Add missing license headers

[Adrien Plazas <aplazas src gnome org>]

commit e4b1d72ca1a3d5093b5da3700a9176284c2132d4
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Thu Aug 3 09:59:10 2017 +0200

    Add missing license headers

 retro-gtk/retro-log.c      |    2 ++
 retro-gtk/retro-rotation.h |    2 ++
 2 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/retro-gtk/retro-log.c b/retro-gtk/retro-log.c
index 070d6b2..3b14fef 100644
--- a/retro-gtk/retro-log.c
+++ b/retro-gtk/retro-log.c
@@ -1,3 +1,5 @@
+// This file is part of retro-gtk. License: GPL-3.0+.
+
 #include "retro-gtk-internal.h"
 
 void
diff --git a/retro-gtk/retro-rotation.h b/retro-gtk/retro-rotation.h
index 2cd673d..cf840b0 100644
--- a/retro-gtk/retro-rotation.h
+++ b/retro-gtk/retro-rotation.h
@@ -1,3 +1,5 @@
+// This file is part of retro-gtk. License: GPL-3.0+.
+
 #ifndef RETRO_ROTATION_H
 #define RETRO_ROTATION_H