Add a new function to compute a MCF using a more general description of
the problem. I call it mcf_refinement because it can start with a
feasible flow (though this is not necessary) and adapt it to achieve
optimality.
Changelog-None: askrene: add a MCF refinement
Signed-off-by: Lagrang3 <lagrang3@protonmail.com>
Any file in this directory which is executable and whose name only
consists of alphanumeric characters, space, '.', '-' or '_' will be
automatically loaded when lightningd starts (unless suppressed with
commandline options).