make: unifdef for other OSes (undefined)

*** 49,61 ****
  #include <sys/signal.h>         /* SIG_DFL */
  #include <sys/wait.h>           /* wait() */
  
  #include <string.h>             /* strerror() */
  
- #if defined (HP_UX) || defined (linux)
- #include <unistd.h>
- #endif
  
  /*
   * Defined macros
   */
  
--- 49,58 ----
*** 347,378 ****
   *              sys_nerr        The size of sys_errlist
   */
  char *
  errmsg(int errnum)
  {
- #ifdef linux
-         return strerror(errnum);
- #else // linux
  
          extern int              sys_nerr;
- #ifdef SUN4_x
-         extern char             *sys_errlist[];
- #endif
          char                    *errbuf;
  
          if ((errnum < 0) || (errnum > sys_nerr)) {
                  errbuf = getmem(6+1+11+1);
                  (void) sprintf(errbuf, catgets(libmksdmsi18n_catd, 1, 127, "Error %d"), errnum);
                  return errbuf;
          } else {
- #ifdef SUN4_x
-                 return(sys_errlist[errnum]);
- #endif
                  return strerror(errnum);
  
          }
- #endif // linux
  }
  
  static char static_buf[MAXPATHLEN*3];
  
  /*
--- 344,365 ----