lots of changes - please read as this may break your build

[Dirk Hohndel]

I just pushed out quite a few changes that were waiting for the a couple
of commits to land in libdivecomputer...

I have been working with Jef on getting a few new features into
libdivecomuter (and improve support for the OSTC) and those (plus his
work to support the Shearwater Predator) are now available in
libdivecomputer master.

The one complication is that as part of these latest addition we decided
to switch the deco/ndl reporting from events to samples (which we both
agree is much better - and Subsurface of course has that information in
the samples, anyway). But that means that there is a hard break here:
libdivecomputer quite reasonably doesn't increment any version number
with every commit and there is no easy way to test if the
libdivecomputer 0.3 development version you have installed is before or
after this change. (let's not turn this into a flame war of how Jef
could do things differently to make our lives easier - I am very happy
that Jef and I are working closely with each other to bring both
projects furtner...). Jef just pushed these changes a couple of hours
ago and I pushed the Subsurface changes shortly thereafter.

What it boils down to:

If you want to compile a Subsurface version that includes commit
99a1903d5058 "Update to the new deco / ndl code in libdivecomputer" you
need a libdivecomputer version that contains the libdivecomputer commit
d5d44c1e0ffd "Convert decostop / ndl to samples" and vice versa. These
two commits are closely related.

What else do you get with the latest master?

- improved plotting of the partial pressure graphs
- support for CNS tracking (so far only for supported dive computers,
  i.e. Uemis SDA and OSTC - others to follow)
- initial support for closed circuit rebreather diving (so far focused
  on the Shearwater Predator (including measured pO2 in the breathing
  loop) and the OSTC (via setpoint) - again, others to follow

This also sets up the infrastructure for us to be able to do our own,
calculated CNS tracking.


Please take a look and test to make sure I didn't break anything while
merging these changes.

Thanks

/D