[Simh] back10 redux

[Johnny Eriksson]

I have now had enough time to spend on my 36-bit tape tool, back10, that
it seems to be time to announce an update.

The code can (still) be found at:

  http://www.pdc.kth.se/~bygg/tops/back10.tar

For now it can:

* read and extract files from backup-10 tapes.

* read and (somewhat) extract files from dumper tapes.  At the moment it
  writes one full page (512 words) for each logical tape record, ignoring
  the file length meta-data.  This will be fixed "soon".
  
* read and extract files from failsafe (!) tapes.  One such tape is
  AP-D481A-SB_1978.tap (BASIC-10 V17E 1978 from trailing-edge).

* write backup-10 tapes, in both interchange and native modes.

* examine tapes, both show the record structure (-s) and peek at data
  in various formats (-p).

If there are other formats, it should be fairly straight-forward to
add them.

This is still very much a work-in-progress.  For instance, the manual
is not yet done.  In fact, it does not even exist.

Enjoy,

--Johnny