Start file transfer if direct connection setup is slow (also fixes Kopete 0.12.6)

[diederik]

When the direct connection setup is slow, KMess should start sending the file data while it still waits for the connection setup to complete.

Bennefits:

• makes sure the file transfer starts earlier if a DC connect is slow, or would fail later (e.g. filewall dropping).
• fixed sending files to Kopete 0.12.6, which does not respond to the transfer INVITE request at all.

A warning message should be displayed so we can debug why file transfers are slow.

[diederik]

I won't fix this in the current SVN version a few day's before the release. aMsn -> Kopete also doesn't work. Will test for gaim as well.