[sldev] Popup ordering patch

[Argent Stonecutter]

The big issue with click-through isn't really having a popup timed to  
come up on top of an existing benign dialog, it's having a lot of  
similar dialogs up at once and clicking through them all to clear  
them... and having one of them take money from you.

For example, this is what people who spam group invites to "pay to  
join" groups depended on... people logging in and having a bunch of  
"You got an IM from FOO" and "BAR has given you an object" messages,  
and clicking "join" accidentally.

There's three classes of dialog that we should be thinking about here:

1. dialogs for which the results are easily reversed, eg: friending.
2. dialogs for which the results are hard or impossible to reverse,  
eg: certain permissions
3. dialogs for which results can include an irreversible loss of  
money or inventory, eg: payment

Then there's a second dimension:

a. dialogs that are triggered only by a user's explicit action. "do  
you really want to do that?"
b. dialogs that are triggered asyncronously.

There should probably be few if any "a" type dialogs, and it should  
be possible for the user to disable most of them, though there's a  
few special cases (like granting someone permission to modify your  
objects) that should be rare and the dialog shouldn't be disabled.

Type A and B dialogs should probably look different.

Class 3 dialogs should probably look different.

I don't think popup ordering should be changed, unless there's some  
kind of clear and obvious effect to clearly indicate that there's new  
dialogs coming in. For example, having a stylized stack with its  
depth proportional to the number of dialogs "below" the displayed  
dialog.