bug#12419: Mouse click changes layout

[martin rudalics]

> We're discussing this in the context of fixing another regression,

... which is not a regression IMHO ...

> so
> I'm willing to trade one regression for another.

I'll come up with a non-regressive fix ;-)

> Wouldn't `asymmetric' handle it acceptably if the small bottom window has
> something like `window-size-fixed' set?

For some value of acceptability, yes.

martin