libmikmod: upgrade to 3.2.0

* 3.3 is only beta
* 3.1.12 was failing to build with texinfo-5, see
  http://sourceforge.net/p/mikmod/mercurial/ci/1fd17189f82561a3a0e343aef05e5cf0b39b8f26/



Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>