MP 0.21 Win: Custom layouts always "restore"

[JohnFredC]

To reproduce:

- Maximize MP
- Create/save a custom panel layout
- Switch to one of the standard layouts
- Maximize MP again, if necessary
- Switch to the custom layout

MP window becomes "Restored", but window control shows "Restore" image

- Click the Restore icon on the MP window border
- Window control changes to "Maximize" image, but XnView remains "Restored"
- Click the Maximize icon on the MP window border again

XnView maximizes, window control displays correct (i.e., "Restore") icon

[xnview]

Right, it's a QT bug, we must wait that they fix it (soon)