Restoring compatibility with old plugins

[Sadrul Habib Chowdhury]

* Casey Harkins had this to say on [01 Dec 2007, 12:04:26 -0600]:
[snip]
> 
> I haven't taken a look yet, but I'm assuming those two revisions (08f54 
> and 2b7518) were the revisions that added the detached UI conversations 
> in place of the hidden conversations. After that was done, there were a 
> number of revisions I made to fix up things that broke:
> 
> 	f881ac75f7e0412344009a6cc0f00318fa750fa0
> 	732917d4f1ac90e4c7e5143bbd59513fd6eef921
> 	bf0838b152a3c0de2a03ee2007286559039c7f22
> 	a29ccbb63a3c059184a3bacefa036a13af45e808
> 	4c59953fd39724c7b48e897585df61dab901c4d2
> 

I think these fixes are in 2.3.1, and they don't need to be reverted.
The result of the fixes is, if I understand correctly, to be able to
deal with unseen/unread messages in a PurpleConversation correctly,
irrespective of whether there's a PidginConversation attached to it or
not.

If anyone is willing to test it, look at the unseen counts and states in
the tooltips and context menus of the docklet and the menutray icon in
the buddy list and see if they are showing the correct values in
different situations.

If there were other fixes in these revisions, then someone needs to take
a closer look, or say what the fixes were for.

Sadrul