TaskDialog implementation - Feedback needed

[Fabian Maurer]

Hello,

As already mentioned in "commctl32: TaskDialog", I'm currently working on a 
full implementation for TaskDialogIndirect.
Now that I have a working foundation, I figured I ask for feedback instead of 
having to rewrite it later.

Since TaskDialogs are very dynamic, the approach is to create a dialog 
template in memory, and then show it as dialog box.

I attached 3 patches which create a small dialog. Though it doesn't do much 
(or anything) yet, it should be very easy to start from there and add all the 
missing functionality piece by piece.

Criticism welcome.

Fabian