the CMake manual promises more than it holds.
Also adding some diagnostics+fixes for zlib, we still assume that it
exists (true on most systems, HDF5 also requires it normally)
see also https://stackoverflow.com/questions/21593
currently it simply converts the whole file content to flow mode.
The nice thing is: It can convert EVERYTHING to flow mode. libfyaml is
the only library that passes the whole YAML test suite
assume that zlib is available for linking. This is usually the case
(zlib is a stable standard library), but there is currently no check
that gives a nice error message or the possibility to use zlib from a
non-standard location
Martin Diehl