Update to new sane libdivecomputer interfaces

Update to new sane libdivecomputer interfaces

This does mean that you have to build subsurface against a new version
of libdivecomputer, and that version is likely going to have various
slightly incompatible changes.  But the new interfaces allow for easily
adding new supported dive computers without subsurface having to be
updated for each new vendor and model, so some slight pain is definitely
worth it this time.

I'm not even going to try to have some backwards-compatible version
here, the libdivecomputer interface changes are so extensive.  Native
enumeration of devices is just the smallest part of it: the constants
and types that libdivecomputer uses now have much nicer names that all
start with DC_ or dc_, so you don't get the kinds of name clashes we had
with "gasmix_t" etc.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>