Fix the decoding of the dive time.
Fix the decoding of the dive time.

The dive time is stored in two separate bytes: one for the number of
minutes, and another one for the hours. Since we only took into account
the first byte containing the minutes, the divetime for dives longer
than one hour was always too short.

glance-/libdivecomputer,Poltsi/libdivecomputer-vms,henrik242/libdivecomputer,henrik242/libdivecomputer,glance-/libdivecomputer