> C-x ^ runs enlarge-window

Silly binding.

 >> Does it work if you set `resize-mini-windows' to nil?
 >
 > No.

First bug.  I forgot that one can invoke `enlarge-window' and
`shrink-window' in the minibuffer window.  I'm not sure though whether these
should have any effect when `resize-mini-windows' is non-nil.

 >>  If I do that here, I can, for example, drag the divider between the
 >> emacs -Q main window and the minibuffer window with the mouse.
 >
 > I can't seem to do that (GNU/Linux, lucid toolkit), no matter what the
 > value of resize-mini-windows is. Works in 23.4, not in trunk.

Second bug (though it should work with >= 2 windows).  I misinterpreted
the semantics of `one-window-p'.

Please test the attached patch.  Resizing miniwindows was hardly tested,
unfortunately.

martin