9 track tapes and block sizes

[Lars Brinkhoff]

Dave Wade wrote:
> The docs for SIMH .TAP files are here:-
>
> http://simh.trailing-edge.com/docs/simh_magtape.pdf
>
> be careful as there are also non-SIMH .tap formats 

Haha, yes very much so.  For the fun of it, people like to mix and match
these options:

- Records padded to even length or not.
- Little or big endian record length metadata.
- 9-track or 7-track data (the latter may have a parity bit).