#64 TLS errors not reported

[Magnus Henoch]

If connecting fails because of a TLS error, the error message is quite unhelpful: magnus.henoch@example.com/nil: connection lost: `nil'

In the process buffer (see jabber-debug-keep-process-buffers) there is more information:

- The hostname in the certificate does NOT match 'example.com'

jabber.el should present this information to the user. (This might involve changes to Emacs)