Add syntax description of MLOCK message to ts6-protocol.txt.

doc/technical/ts6-protocol.txt

@@ -452,6 +452,28 @@ parameters: server mask, hunted
 
 Remote LUSERS request. Most servers ignore the server mask, treating it as '*'.
 
+MLOCK
+charybdis TS6
+source: services server
+parameters: channelTS, channel, cmode changes, opt. cmode parameters...
+propagation: broadcast (restricted)
+
+Propagates a channel mode lock change.  
+
+If the channelTS is greater (newer) than the current TS of the channel, drop
+the message.
+
+On input, only the limit on parameters per line restricts how many cmode
+parameters can be present. Apart from this, arbitrary modes shall be
+processed. Redundant modes may be dropped. For example, +n-n may be applied and
+propagated as +n-n, -n or (if the channel was already -n) nothing, but not as
++n.
+
+The parameter for mode -k (removing a key) shall be ignored.
+
+An MLOCK message with no modes disables the MLOCK, therefore the MLOCK message
+always contains the literal MLOCK for simplicity.
+
 MODE
 1.
 source: user