SDL2_gfx tabbing/license cleanup

src/SDL2_gfx.cs

@@ -1,3 +1,31 @@
+#region License
+/* SDL2# - C# Wrapper for SDL2
+ *
+ * Copyright (c) 2013-2021 Ethan Lee.
+ *
+ * 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.
+ *
+ * Ethan "flibitijibibo" Lee <flibitijibibo@flibitijibibo.com>
+ *
+ */
+#endregion
+
 #region Using Statements
 using System;
 using System.Runtime.InteropServices;