Implement appending to chat logs on demand

[valerio]

At the moment, the chat logs (XML, HTML or text) are saved when the chat closes. If the computer hangs, the X server crashes, or KMess hangs or crashes, all current chat logs are lost.

KMess should add new messages to the log files as they arrive. At least it should do it for the more important XML logs.

This would bring the following consequences:

• the chat logs will always be up-to-date (no data loss),
• there will be no delay when closing a chat tab

As a very little downside, we'll have to keep the file fully readable at any moment (ie we'd have to remove the footer, add the new message then add the footer again).

An (worst) alternative could be to save every 30s or so.

 Reference topic

[diederik]

I'm all in for saving with an interval timer! :) Saving at every typed chat message seams a bit resource intensive to me.

[valerio]

Implemented recently, in the chathistory-new branch.