bug#24651: 25.1; frame-inherited-parameters only partially works

[martin rudalics]

>>> When a val is nil, it
>>> won't override a default parameter whose value is non-nil.  But I never
>>> figured out what inherited parameters are useful for in the first place
>>> so maybe this is of no importance.
>
> They were introduced so as to associate specific frames with specific 
emacsclients.

And there a non-nil parameter in 'default-frame-alist' is supposed to
override a nil parameter in 'frame-inherited-parameters'.  Such that
with emacs -Q setting

(setq default-frame-alist '((alpha . 50)))
(setq frame-inherited-parameters '(alpha))

in *scratch*, C-x 5 2 will produce a semi-transparent frame.

martin