Updated usage messages for command-line utilities to reflect new options.

Updated usage messages for command-line utilities to reflect new options.
Updated manual to reflect reality (e.g. usage messages, '-p port' not actually
  implemented, sprinkle references to '-i keyfile').
(I've put "Release 0.53" in the messages; let's hope this doesn't cause a
  flood of "where is 0.53?" email.)
I don't guarantee that the result is entirely sane and sensible in all
  respects, but it is at least consistent.

git-svn-id: svn://svn.tartarus.org/sgt/putty@1951 cda61777-01e9-0310-a592-d414129be87e