This code was string-by-string applying changes from http://www.di.uevora.pt/~spa/software/gprolog-cx_1.2.18-16.tar.gz to GNU Prolog 1.4.1 source code.
This work was done in 2012 year and now I not remember what I do and which problems I get.
If you want to build this code with GNU Prolog then you must read `doc-cx/BOOTSTRAP-NOTES' file first.