PDAL/PDAL — pull request #546 by gadomski (2014-10-24 22:09:22+00:00)
Title: Clean up cmake's zlib logic

Previously, we still only linked against zlib if the cmake variable WITH_ZLIB was true, but now that zlib is a required dependency, we should always link against its libraries.

Additionally, use the REQUIRED flag for the zlib find_package.