Finally documented the last remaining commands, some of which
are not intended for end users, others of which had been overlooked.
All commands (parser and otherwise) plus aliases and configset
variables, now have help files available.
reworked heading of configset_variable help files...
now auto-extracted from release source instead of
re-parsing configshow output, more info and more consistent
removed file_header, never used and contained bad info
make manifest reflect files deleted yesterday
change comment reference from parser_data.pl to CommandProps.pm
(getresp) Treat the 552 error code as a fatal error.  If a 552 is received
for a RCPT TO because the message is too large, DATA will fail.
Exim will return a 552 for too many recipients in some cases, in
which case DATA will fail also.
obsolete variable removed, some text put into help files
bug fix for command_legal() - missing "exists" test caused hash keys to be added
added new command_list() to return all keys of %commands and %aliases