Add historical notes on QIC tape drives and fix a couple of issues in mt(1).

o Density code 0x5 is also known as QIC-11, and should have a footnote

reference.

o Add notes on QIC tape drives from the bug report. These may help anyone

trying to use a QIC drive.

o Take out a "more more" instance found by igor.
o Bump the man page date.

The PR is 14 years old, so it's past time to retire it.

PR: doc/53596
Submitted by: tedm@toybox.placo.com
Reviewed by: bcr
Sponsored by: Spectra Logic