[Mono-winforms-list] MDI fixes

[Ernesto]

Hi,

I've been working on several issues with the MDI code and I would like 
someone to take a look at the patches I've sent and -hopefully- merge 
and close some bugs.

First, bug #328019. I think the patch is ok and the bug can be closed.

Next, bug #325473 is a duplicate of bug #325434. I've sent a patch for 
bug #325434 that fixes the reported problem and others somehow related 
issues; cosmetic mainly. This patch also fixes bug #325433.

I need comments about one small change in ActivateChild(). Looks 
dangerous, but I think it's the cause of the many issues reported in 
#325434 and #325473.

The rest is pretty innocuous.

If the patch is ok, #325433, #325434 and #325473 can be closed.

Regards,
Ernesto