[jabber.el] Emacs 23.1 required; removed sha1.el and hex-util.el

[Magnus H. <mag...@gm...>]

Hi all,

I just pushed a change that removes sha1.el and hex-util.el from
the compat subdirectory.  Those files have been present in GNU Emacs
since version 22.1, which was released in 2007, so I hope that's a safe
move.

I changed the README to say that 23.1 is now the minimum required
version.  23.1 contains a change to dns.el that makes it possible to
make SRV queries, which is necessary to connect to e.g. Google Talk
without manual configuration.  I'm still considering whether to remove
the condition-case in jabber-srv-targets - doing so would break things
for people who use Emacs 22 but know what they're doing, but not doing
so might leave Emacs 22 users with failing connections and no good
explanation.

If you think it's valuable to support older Emacs releases, I'm open to
be persuaded.

I don't know how this affects XEmacs users - reports are welcome!  I
also have a nagging feeling that Windows users are left without SRV
support...

Regards,
Magnus