Don't include zlib files directly. That's very nasty!

zlib is now ivoked in a more common way (we link against it :-).
The build process inclusion is probably not the final one, but it works
for me for zlib 1.1.4 and 1.2.1 in command line builds.

PR: 25578


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@102370 13f79535-47bb-0310-9956-ffa450edef68