Adjust the baudrate for Unix systems.
Adjust the baudrate for Unix systems.

The termios interface does not support setting a baudrate of 256000 bps,
but using the nearest supported baudrate appears to work fine too.

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