mod_websocket: Fire pre-session-close event (fixes #1800) This event was added in a7c183bb4e64 and is required to make mod_smacks know that a session was intentionally closed and shouldn't be hibernated (see fcea4d9e7502). Because this was missing from mod_websocket's session.close(), mod_smacks would always attempt to hibernate websocket sessions even if they closed cleanly. That mod_websocket has its own copy of session.close() is something to fix another day (probably not in the stable branch). So for now this commit makes the minimal change to get things working again. Thanks to Damian and the Jitsi team for reporting.

Structure of a stanza:


stanza {
	--- properties ---
	tags -- array of tags
	
	--- static methods ---
	iq(attrs) -- 
	
	--- read-only methods ---
	reply -- return new stanza with attributes of current stanza
	child_with_name(string name) -- return the first child of the current tag with the matching name
	
	--- write methods ---
	tag(name, sttrs) -- create a new child of the current tag, and set the child as current
	up() -- move to the parent of the current tag
	text(string) -- append a new text node to the current tag
}