variables. It was no longer true (given that we support them in SSH-2 now),
and the new situation was probably too complex to explain in an introductory
chapter. And the utility of setting them seems to be marginal these days given
the lack of server support.
[originally from svn r4679]
added an introduction to public key authentication, and made a
couple of changes in intro.but. Transatlantic flights have some uses
after all.
[originally from svn r1146]
