Alt+Tab switch highlighting

[Jannis Pohlmann]

Hey Olivier/Ori,

I just noticed that, when switching between windows using Alt+Tab, the
icon of the windows having the focus is not highlighted in any way. This
is somewhat annoying and may be confusing, because reading the text
above the icons takes much more time than just looking at which icon is
highlighted (colored background e.g.).

What do you think?

- Jannis