Really prevent time travel in planner dive edit

Commit c92e4535a6de "Prevent time travel in planner dive edit" almost got
it right but had a stupid think-o. This commit should fix it the right
way. If the duration that is passed in is before the previous timestamp,
then this is most likely intended to be a relative time.

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

Coding style in deco.c.
Unneccessary if clause in profile.c (the loop starts with i = 1)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Improve travel logic code for the ascent in the planner

This shouldn't change the the actual stops we do or the travel time how we
get there, but it makes the code more logical. From the end depth of the
planned dive we have ONE transition to the first stop depth (which may be
the surface). And then for every stop we (potentially) have a wait and
travel to the next stop.

Once we are in the while loop, we know that we are at a stop level, so
there is no point to keep checking if we first need to transition to the
stop.

It does create one additional improvement: if we don't need any stops at
all, then we don't transition to the first stop and then from there to the
surface. We do it in one step. The overall profile / traveltime remains
the same, we just drop one intermediate sample on the way.

This also improves a few ugly (and in one case, wrong) debug statements.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix the deco calculation in the dive planner

The existing code incorrectly started all calculation at the depth at the
end of the first segment. So if you went to 50m in 5min in your first
segment, you incorrectly got 5 minutes at 50m (instead of a progression
from 0 to 50m, over 5 minutes).

This commit fixes that and now gives us planned dives that then match what
is shown in the profile.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Do planned deco stops in multiples of 1 minute

We may want to make this configurable, but I haven't seen any software
that doesn't do deco stops in full minutes.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Set a default surface pressure for dive plan and allow simplistic print

This commit makes sure we have a reasonable default surface pressure (we
need an input field for that).

It also adjusts the debug level settings so that compiling this with
make CLCFLAGS=-DDEBUG_PLAN=3
will print out an almost usable dive plan.

This is of course still lacking air consumption calculations and will show
deco stops that we just transit through (if the ceiling lifts far enough
during the transition to an intended stop that this stop can be skipped;
this sometimes happens for the first stop (haven't seen it for a later
one). But it's better than nothing, I guess.

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