modeline justified but for more that real terminal width

[Dan Jacobson]

Let's examine how emacs up to at least "22.0.50.1" is nonchalant about
wasting space in the modeline even when it means that vital words get
cut off:
-BBB:---F1  eeeeeeeeeeeeeeeeeeeeeeeeeee   All L1      (Fundamental Compil

The fluffy spaces around the "All L1" are what are bothering me.

If this were a paragraph, I would first do fill-paragraph, then
justify, then finally present the modeline to the user.

Test with (compile "sleep 4444") and varying lengths of
(switch-to-buffer "eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee")