updates to Subsurface and libdivecomputer

[Dirk Hohndel]

Thanks to Linus and Anton we have an updated Subsurface-branch for 
libdivecomputer.
This goes along with an update to Subsurface itself to adjust to the 
modified API for our serial code.

I’ve had problems with the native Bluetooth code for a while and feel
like I can’t quite figure out where the culprit is. I only had a chance to
test this on my Mac, though, and Bluetooth has always been a challenge
on the Mac.

I’d appreciate if some of you with Bluetooth dive computers could give
this a try and let me know if things work on Windows, Linux and Mac.

(I’ll make new daily builds available)

Thanks

/D