Rework the parser a bit to be more sane when it comes to newline and comma

Rework the parser a bit to be more sane when it comes to newline and comma
handling. In expansion lists we want that commas and newlines are allowed
but optional. In the neighbor, group and rdomain blocks statements need to
be newline separated but neighbor 192.0.2.3 { descr "test-peer" } is allowed.
OK sthen@ benno@