Instead of having people treat latitude and longitude as separate
things, just add a 'location_t' data structure that contains both.
Almost all cases want to always act on them together.
This is really just prep-work for adding a few more locations that we
track: I want to add a entry/exit location to each dive (independent of
the dive site) because of how the Garmin Descent gives us the
information (and hopefully, some day, other dive computers too).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>