Added zlib license for Steam Controller headers

src/joystick/hidapi/steam/controller_constants.h

@@ -1,8 +1,23 @@
-//===================== Copyright (c) Valve Corporation. All Rights Reserved. ======================
-//
-// Purpose: Defines constants used to communicate with Valve controllers.
-//
-//==================================================================================================
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 2020 Valve Corporation
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
 
 #ifndef _CONTROLLER_CONSTANTS_
 #define _CONTROLLER_CONSTANTS_

src/joystick/hidapi/steam/controller_structs.h

@@ -1,8 +1,23 @@
-//===================== Copyright (c) Valve Corporation. All Rights Reserved. ======================
-//
-// Purpose: Defines methods and structures used to communicate with Valve controllers.
-//
-//==================================================================================================
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 2020 Valve Corporation
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
 #ifndef _CONTROLLER_STRUCTS_
 #define _CONTROLLER_STRUCTS_