Removing GtkLookAndFeel

[Dalibor Topic]

Hi all,

while syncing code around, I came accross the 
gnu/javax/swing/plaf/gtk/*.java classes, which do not seem to be used 
anywhere in GNU Classpath.

So I'd propose removing the unused classes, but keeping the icons 
subdirectory around, since that one is used by javax.swing.

If there are no objections, I'll check in a patch.

cheers,
dalibor topic