Merge branch 'weight' of git://subsurface.hohndel.org/subsurface

Merge branch 'weight' of git://subsurface.hohndel.org/subsurface

Pull weight management from Dirk Hohndel:
 "This is the fifth or sixth version of this code, I'm begining to lose
  track.  I still struggle with the balance between code duplication and
  unnecessary indirectness and complexity.  Maybe I'm just not finding
  the right level of abstraction.  Maybe I'm just trying too hard.

  The code here is reasonably well tested.  Works for me :-)

  It can import DivingLog xml files with weight systems and correctly
  parses those.  It obviously can read and write weight systems in its
  own file format.  It adds a KG/lbs unit default (and correctly stores
  that).

  The thing I still worry about is the code in equipment.c.  You'll see
  that I tried to abstract things in a way that weight systems and
  cylinders share quite a bit of code - but there's more very similar
  code that isn't shared as my attempts to do so turned into ugly and
  hard to read code.  It always felt like trying to write C++ in C..."

* 'weight' of git://subsurface.hohndel.org/subsurface:
  Add weight system tracking

Fix up some trivial conflicts due to various renaming of globals and
simplification in function interfaces.