H316, NOVA, PDP11, PDP8, PDP18B, KX10: Record Sequential updates consistently

Devices that do single character I/O could be attached to non seekable
host OS devices (tty, pipes, etc.) and thus shouldn't count on fseek()
and ftell().  These DEVICEs on these simulators do single character I/O
and easily can update their POS REGisters to reflect how much data has
been emitted.  Changing such a REGister will have no  useful effect
when attached to a non seekable file.

PDP10/kx10_pt.c

@@ -181,12 +181,12 @@ t_stat ptp_svc (UNIT *uptr)
         return SCPE_OK;
     }
     fputc (uptr->CHR, uptr->fileref);                       /* print char */
-    uptr->pos = ftell (uptr->fileref);
     if (ferror (uptr->fileref)) {                           /* error? */
         perror ("PTP I/O error");
         clearerr (uptr->fileref);
         return SCPE_IOERR;
     }
+    uptr->pos = uptr->pos + 1;
     return SCPE_OK;
 }