libmspub depends on zlib

Change-Id: I3024693698f85ef1c2bbb7fb6ee968a0d5ba6359
(cherry picked from commit 2116f1cfb31e5fcf829c2f101cd878a32b56c365)
Reviewed-on: https://gerrit.libreoffice.org/13537
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>