Add IBM TS1160 density codes to libmt and the mt(1) man page.

Add IBM TS1160 density codes to libmt and the mt(1) man page.

These are taken directly from the density report from a TS1160
tape drive.  (Using mt getdensity)

A TS1160 drive stores 20TB raw (60TB with compression) on a JE tape.

lib/libmt/mtlib.c:
	Add 3592A6 encrypted/unencrypted density codes, and bpmm/bpi
	values.

usr.bin/mt/mt.1:
	Add 3592B5 encrypted/unencrypted density codes, bpmm/bpi
	values and number of tracks.  Bump the man page date.

MFC after:	3 days
Sponsored by:	Spectra Logic