cut at 20 January version of DSN document

use wordinclass() abstraction for searching classes

allow $#local $: @ /filename

more DSN hacking

improved debugging

improve DSN handling somewhat + some bug fixes

get ORCPT= ESMTP DSN parameter working

clean up several small problems with file delivery, error detection,
and return receipts

convert to new DSN draft

check for "<<>>" etc as equivalent to "<>"

first cut at DSN implementation

use -s flag on dequote map to indicate space substitution

use SpaceSub option value for space replacement in dequote map

make all flags be printed in hex rather than octal (except file modes)

break out special local mail processing (e.g., mapping to the
"prog" mailer) onto separate mailer flags

move entry/exit debugging to 21.1

avoid null pointer dereference in debugging code

don't print size parameter in error messages during parsing

make default $#error number 553 instead of 501

try to make sure that path-addrs always have <angle brackets>

avoid core dump on $> with no argument; fix sameaddr to avoid
excessive FALSE values

parameterize maximum recursion depth (compile time only)

avoid core dump if getctladdr() returns null

fix uid-dependent non-equivalence of addresses