syntactic sugar: support range notation such as

syntactic sugar: support range notation such as
    1.2.3.4/24{5,6,7,10-20,60-90}
for set of ip addresses.
Previously you needed to specify every address in the range, which
was unconvenient and lead to very long lines.
Internally the set is still stored in the same way, just the
input and output routines are modified.

Manpage update still missing.

Perhaps a similar preprocessing step would be useful for port ranges.

MFC after: 3 days