[CMake] Telling CMake to use zlibConfig.cmake instead of the Findzlib.cmake

[Brad King]

Alan W. Irwin wrote:
> A module that gives header and library information for a package does sound
> most useful, and, in fact, we could use that kind of module for the PLplot
> project (especially if the module is automatically generated from the
> install information that CMake already has access to) so I am looking
> forward to when that kind of module is properly documented.

It is documented in the Mastering CMake book available here:

http://www.cmake.org/HTML/Documentation.html
http://www.kitware.com/products/cmakebook.html

-Brad