Close button overlaps last tab

[sander]

When many tabs are opened, the close button overlaps the last tab. The last tab should ever go under the close button.

[Mats (matsben)]

The current code is a hack and at that time there was no way to identify mouse clicks on elements in tabs. I've seen that there is a [$w identify x y] command added which returns the name of the element being clicked, but I can't see it in the tile docs.

[Mats (matsben)]

Added tab layout with close cross. It isn't perfect, but seems it works. When the number of tabs don't fit anymore it is up to the ttk::layout algorithms to handle this. At least there is no close button outside the client and tab area anymore.