Some UMC uses listbox rowes with less than 20 pixes which caused images
to be resized to x - 20 which is negative and resulted into huge
positive numbers.
Modified the WML to return 0 in these cases and also added protection in
the engine to ignore those images. (The latter is needed since people
can create their own themes which might have this problem as well.)
Fixes bug #14525 and probably bug #14002.
This shows the scrollbars when a window doesn't fit, the code is only
lightly tested but initial tests seem to work. More testing is needed
especially on the MP lobby.
It still shows some scrollbars too often, which will be fixed later.
Fixes bug #13180.
The functions stretch a surface based on the first row/column. This
looks better for the widget borders as scale_surface and should be
faster (not tested). Added the option to the widget library to use
these functions and convert the window borders to use the new option.