BT support, brief tests

[Dirk Hohndel]

Hi Claudiu,

I did some quick tests. Applied the libdivecomputer patches as they are
and added a small patch to install the custom_serial.h file, added the
patches to subsurface and gave it a shot.

UI seems to work, I see my local device, I see the OSTC Sport, I can pair
it and then it shows that it's paired and allows me to save things.

But then when I click download it shows "initializing" and everything
hangs. Or at other attempts it shows "0%" and hangs.
Can't close the dialog, have to kill Subsurface.

Running this under the debugger it seems to be hanging in qt_serial_open
on the loop.exec() call (in the Download thread).  We definitely need to
start a timer and connect it to the quit slot of that connection as well.

I tried a few different things but I can't seem to make it past that
loop.exec() call. Not quite sure where to take this, next.

/D