.NET 3.5 fix

src/LPUtf8StrMarshaler.cs

@@ -80,7 +80,7 @@ namespace SDL2
 				throw new ArgumentException("ManagedObj must be a string.", "ManagedObj");
 			}
 			var bytes = Encoding.UTF8.GetBytes(str);
-			var mem = SDL.SDL_malloc((IntPtr) bytes.Length + 1);
+			var mem = SDL.SDL_malloc((IntPtr) (bytes.Length + 1));
 			Marshal.Copy(bytes, 0, mem, bytes.Length);
 			((byte*)mem)[bytes.Length] = 0;
 			return mem;