who has two different incompatible copies of zlib installed:
(in /usr and in /usr/local).
cmake errorneously chose *.h file from /usr/local/include,
while zlib.a/zlib.so from /usr/lib/. Compilation failed
because of a missing symbol gzopen64.

modified:
  @ cmake/zlib.cmake
  Removing the line (as suggested by Vlad) which made cmake choose
  the wrong library.
  Note: this line used to be a hack for old HP machines,
  it's not needed anymore.