Send an IRC listener user their own TOPIC, MODE and KICK once (closes #143)

The service sends a TOPIC, MODE or KICK to every channel member, the
issuer included, and the IRC listener also echoes it to the issuer's
connection, so an IRC listener user got each of their own changes
twice. The relay now drops one whose sender is the connection's own
nick, as it already does for PRIVMSG, NOTICE, JOIN, PART, NICK and
QUIT. The direct echo stays: it carries the real hostmask and arrives
in order. The README MODE section no longer describes a second copy.

Model: opus-5-5

README.md

@@ -1019,9 +1019,8 @@ On the IRC listener, `MODE #channel <modes> [values...]` takes several letters
 in one string, e.g. `MODE #general +mt-i` or `MODE #general +ov alice bob`. It
 accepts `i`, `m`, `n`, `s`, `t`, `o` and `v` (with a nick) and `H` (with bits
 from 1 to 40 when setting), but not `b`, `k` or `l`. A letter whose value is
-missing is skipped. The changes made are echoed to the operator's connection and
-also sent to every channel member, the operator included, as one `MODE` line,
-e.g. `+o-v alice bob`.
+missing is skipped. The changes made are sent to every channel member as one
+`MODE` line, e.g. `+o-v alice bob`; the operator gets that line once.
 
 **Channel errors:**