@lazedo - yhe function open_memstream() seems to be unavailable for various *BSDs, MacOSX, Unix'es versions:

* https://www.gnu.org/software/gnulib/manual/html_node/open_005fmemstream.html

A solution would be to include an alternative implementation, like:

* http://piumarta.com/software/memstream/

As a quick solution I am going to disable it for non-Linux. You can choose another variant and push into the git repo.