So I fixed the building of the new NLS files. One weird thing I found was classes/res/es/mmres_es.c which was totally different from the other NLS mmres_*.c files. Lewis, where did you find that? I take it you have no objection to changing it to (ignoring the license header)

#include <os2.h>

PSZ queryLanguage()
{
  return "Español";
}

I'll push my changes shortly, mostly makefiles, if no objections.