Revert back to a standard baudrate on Unix.
Revert back to a standard baudrate on Unix.

The linux USB CDC-ACM driver, which is used by the Mares Icon HD
interface, doesn't support the ioctl's to configure a custom baudrate.
But since the actual baudrate doesn't seem to matter at all, we revert
back to the nearest standard baudrate.

Because custom baudrates are confirmed to be supported on Windows and
Mac OS X, those platforms can keep using the non-standard baudrate.

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