Support both the OC and CC gas mixes.
Support both the OC and CC gas mixes.

The Shearwater Predator has two different sets of gas mixes for OC
(Open Circuit) and CC (Closed Circuit) mode. Since the dive mode can
be switched during the dive (e.g. in a bailout scenario), there is no
easy way to select one of both sets. With this change, both sets are
returned. It's not a perfect solution, but for CC dives it's already
an improvement.

venkateshshukla/libdivecomputer,glance-/libdivecomputer,josh-wambua/libdivecomputer,josh-wambua/libdivecomputer,henrik242/libdivecomputer,Poltsi/libdivecomputer-vms,henrik242/libdivecomputer,venkateshshukla/libdivecomputer,glance-/libdivecomputer