Framed in a full rework of the cylinders info import management, this
funcs will be used in next patches.
Functions merge_cylinder_type(), merge_cylinder_mix() and
merge_cylinder_info(), have been shamelessly copied from dive.c as they
have been removed by 162767aa dated 2017-03-11 just when I was going to
use them.
Macros MERGE_MAX() and MERGE_MIN() have just been copied from dive.c,
but they could be moved to dive.h so they could be used elsewhere if
needed.
Signed-off-by: Salvador Cuñat <salvador.cunat@gmail.com>
36658d87f3