For KMZ reading we use the minizip contrib package that comes with zlib (see
DEPENDENCIES). To avoid compiling third-party sources into our code, we build
minizip as a separate library.

There are some local modifications to the minizip code to avoid symbol clashes
with other projects that might statically link both libkml and its
dependencies with other libraries dependent on minizip. These can be seen by
diffing r655 with r656.

