bug#15046: 24.3.50; Extra Line under minibuffer in Mac OSX fullscreen

[martin rudalics]

> The minibuffer/echo area window is just another window, so why would
> Emacs treat it specially?  If other windows can have partially visible
> lines, why cannot the minibuffer window have them?

We have to handle minibufferless frames anyway.  But there's no reason
to not optionally give the space to the minibuffer.

martin