Update the function to create the dive duration string in a way that
it can be used also in info and stats tab and added some more flexibility.
Changed layout for <1h freedives to "0:05:35" (w/o units) or "5:35min"
(with units and :) or "5min 35sec" (with units with space).
Add a new function to create the surface interval string.
Completely remove old function get_time_string() and get_time_string_s().
Signed-off-by: Stefan Fuchs <sfuchs@gmx.de>
e6d884cf26