Update libsdl version

packages/libsdl.rb

@@ -3,7 +3,7 @@ require 'package'
 class Libsdl < Package
   description 'Simple DirectMedia Layer is a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware via OpenGL and Direct3D.'
   homepage 'http://www.libsdl.org'
-  version '1.2.15'
+  version '1.2.15-1'
   source_url 'http://www.libsdl.org/release/SDL-1.2.15.tar.gz'
   source_sha256 'd6d316a793e5e348155f0dd93b979798933fb98aa1edebcc108829d6474aad00'