Make dive mode detection more advanced In commit a09b1855d656, a RTE function was factored out, that was used to detect dive mode vs. surface mode. In the hunt for the time difference bug between stopwatch and dive time some progress was made, but its still not totally right. Add some old logic back, that seems reasonable. A pool test after this commit shows some improvement, but still there is some random difference between stopwatch and dive time. Things like perfectly in sync for 20 min. surface shortly, and descend again in the same dive. Now, the was a 1 or 2 second difference. Signed-off-by: Jan Mulder <jlmulder@xs4all.nl>