Implement non-standard SEEN-BY and PATH line creation/parsing logic as

requested by Joe (1:249/303), Wilfred (2:280/464) and Michiel (2:280/5555) for
their little 3-node inter-zonal FTN:
"Zone Blind" option (enabled in echofg->Toggle Options or by adding a line
containing the string "ZONE_BLIND" to the sbbsecho.cfg file). This option
causes zones to be ignored (back to the 2D addresses of the 80s) when parsing
and generating SEEN-BY and PATH kludge lines in echomail messages.
Incremented version to 2.23.