Print the end temperature of the dive

Currently we print the temperature every five minutes. Especially with
dive computers that keep rather frequent temperature samples that means
that we have one more interesting data point that we don't label: the
surface temperature at the end of the dive.

This patch adds some logic to try to print the last temperature sample
that was recorded before the dive ended - unless that same value has
already been printed (to avoid silly duplications on dive computers with
less frequent sampling)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>