This template function reads back links as written by writeLinks<>()
INSERTER
must have operator() (LINK*)
(for example, class LinkInserter
)
LINK
must be default constructible and have a method readFrom(istream&)
For each couple of node addresses read from the stream, a new link is constructed, and attach
ed to the respective nodes in memory (whose address is retrieved via where
). Then the link is passed to ins()