GitLab

* strerror/perror now call _kernel_last_oserror and use result
  if errno is unknown.
* _sys_open calls error-returning form of OS_Find so
  _kernel_last_oserror can return something meaningful after
  fopen fails
* All file handling calls set errno to -1 if a _kernel_osfind/
  _kernel_osgbpb etc call returns an error
* These three changes mean that the code sequence

         if ((fp = fopen(file, "rb")) == NULL) {
            perror(progname);
            return 1;
         }

  will now say something useful rather than "No error (errno=0)"
  This could now be used by socklib to get perror to work
  with errors generated by the Internet module.
* ANSILib now outputs proper messages, not just tokens.