Replace Poseidon example dive log files in dives directory

The present example files have dives with some unusual
characteristics due to the fact that the dive pushes the
limits of the Poseidon recreational rebreather.
Replace these example files with a dive that does not have
any unusual characteristics. This facilitates debugging of the
Poseidon code. The xml file represents the same dive as the two
text files. The xml file will ultimately be removed.

Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Remove code that zeroes out duplicate oxygen sensor and temperature values

Remove the code that changes all duplicate oxygen sensor, setpoint and
temperature values from a dive log to zero. One of the motivations is
that a zero setpoint value indicates an Open Circuit dive segment, not
Closed Circuit Rebreather. The code in dive.c is removed and the comments
for the corresponding restoration code that restores the last known values
into sensor or temperature with zero values is [fill_o2_values()
in profile.c] is changed to apply to the present situation.

Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't call strdup on NULL by mistake

Hunting down a different issue I managed to cause a crash here when trying
to copy a string that ended up being NULL.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>