Audio ports are sorted using PBD::naturally_less.
PBD::naturally_less is also used as compare function
for port-lists, port-sets, and port-maps.
So in sets and maps, the function is used to test
for uniqueness. This lead to issues since naturally_less
treats whitespace and underscores as identical.
While it was possible to have routes named "Audio_1",
and "Audio 1", this resulted in missing ports for one
of the routes.
see also 60ff3ef764
8e5af55ae5