[JDEV] Simple disco (JEP-0030) implementation for jabberd-1.4

[Jacek Konieczny]

Hello,

I guest most tkabber users noticed ugly result of "Discovery" function,
which defaults to query the server the user is logged to. This is
because most popular jabber server (jabberd-1.4.x) doesn't support
disco.

I have had implemented JEP-0030 in my GG transport, but then I missed
disco in the jabberd even more. I also inted to make JEP-0038
(statistics gathering) implementation for jabberd-1.4.x, but it seems
useless for tkabber user unless disco is also available (the only way
I found to activate stats support in tkabber is to use disco).

So I wrote it. The patch available at:
	http://www.bnet.pl/~jajcus/jabberd14/mod_disco.patch
adds mod_disco module to jabberd's jsm. This is patch against current
jabberd14 CVS tree, but it should work with last official jabberd
release too.

mod_disco uses existing browse configuration (<browse/> tag in jabber.xml)
for http://jabber.org/protocol/disco#items queries and may use new
<disco/> tag for http://jabber.org/protocol/disco#info queries.

If there is not <disco/> element in the configuration mod_disco sends
reply containing only the <identity/> element with name taken from the
server's vCard. Such <identity/> element is also created if the <disco/>
configuration element doesn't contain any <identity/> tag.

The <disco/> element in jabber.xml file (in <jsm/>) should look like this:
<disco>
	<feature var="iq"/>
	<feature var="message"/>
	<feature var="presence"/>
	<feature var="presence-invisible"/>
	<feature var="jabber:client"/>
	<feature var="jabber:server"/>
	<feature var="jabber:iq:auth"/>
	<!-- 
		...
		all other namespaces supported by the server 
		...
	-->
</disco>

Greets,
	Jacek