Subsurface update for upstream libdivecomputer changes

[Lubomir I. Ivanov]

hi Linus,

is it OK if i bring back these two declarations?

.serial_set_halfduplex = NULL,
...
.serial_set_halfduplex = NULL,

https://github.com/Subsurface-divelog/subsurface/commit/f5e2a17e7d0fa041590ecdc7da3b970cc15537bd

because my g++ 5.3.0 is not happy that the there are missing / out of
order initializers.
"sorry, unimplemented: non-trivial designated initializers not supported"

to my understanding the change will still work.

thanks
lubomir
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