Virtual Power - included patch from Mark Liversedge & corrected bug
with his help.
GSC-10: Check dual sensor 4th and speed-only sensor (which is rare) as
5th.
This means that an all-Garmin setup (ANT+ stick, GSC-10 sensor) will
always work. A speed-only sensor is almost useless in GC real-time
mode anyway, because speed-only sensors tend to run off the front
wheel which will be stationary on a trainer. Fix pointer problems with
device controller/config.
Fixes#219
