Ok, if I knew more German, the comment might have clued me in

I uncommented the #include <unistd.h>, commented the #include <getopt.h> added a couple of LIBS and the compile finished.
Have to test later as have to go out.
There's still the problem of it wanting to be installed to an absolute location, /usr/local by default, to find its data.
German comment,
#if HAVE_GETOPT
/* Laut man-page muss man <unistd.h> includen, wenn man getopt() verwenden
will. Laut gcc <getopt.h>. gcc sitzt am lõngeren Hebel... */
#include <unistd.h>
//#include <getopt.h>
#endif
I should have looked at the headers too, it's how I fixed the ngettext() problem I also had.