VPM support

[Henrik Brautaset Aronsen]

We've talked about this earlier, I thought I'd bring it up again.

When talking with my tec diving friends about what they miss in 
Subsurface, most of them mention VPM [1] support.  The DR5 have VPM 
support, so we might be able to get hold of the algorithms in C from HW.

What do you guys think?

Henrik

[1] http://www.hhssoftware.com/v-planner/vpmdetail.html