trying to fix audio/milkytracker, does not compile since zlib 1.2.4 import

[Emanuel Haupt]

Milkytracker currently fails to build on FreeBSD 9.1 and I am not sure
if it is related to the import of zlib 1.2.4 with 900010.

Build log:
http://people.freebsd.org/~ehaupt/misc/milkytracker/milkytracker-0.90.85_2.log

Upstream bug report:
http://forums.modarchive.org/index.php?topic=3389.0

Any help fixing the build would be appreciated.

Emanuel