Updates to handle old and broken tapes.

[larsbrinkhoff]

if you see "?Tape record too short" it probably means a tape file header was invalid. There may still be valid files after the damaged one, so this makes itstar skip the bad file and try the next.

CC @eswenson1

[larsbrinkhoff]

Widening the scope of this pull request.

• Continue extracting files even if there's an error mid way.
• Handle old style 1-bit year timestamps. Typically in the range 1970-1973.

CC ToTS people, as this may be useful to you. @lisper, @Devon7.

[larsbrinkhoff]

Add -E to use the E-11 tape image format, which doesn't pad records with an odd number of frames. This format is used by (some?) ToTS tape images.

Add -O to write a six-word file header rather than seven words. 1973 vintage SALV 9 will barf on the latter.

[larsbrinkhoff]

I see some tape images have 7-track data, and also have the record length in big endian format. I'll add support for those too.