Complete rewrite of the packet log censoring code.

Complete rewrite of the packet log censoring code.

Because the upcoming connection sharing changes are going to involve
us emitting outgoing SSH packets into our log file that we didn't
construct ourselves, we can no longer rely on metadata inserted at
packet construction time to tell us which parts of which packets have
to be blanked or omitted in the SSH packet log. Instead, we now have
functions that deal with constructing the blanks array just before
passing all kinds of packet (both SSH-1 and SSH-2, incoming and
outgoing) to logging.c; the blanks/nblanks fields in struct Packet are
therefore no longer needed.

git-svn-id: http://svn.tartarus.org/sgt/putty@10071 cda61777-01e9-0310-a592-d414129be87e