bug#22000: Patch addressing the menu-bar frame-resize interaction

[martin rudalics]

> Iʼve tried the patch now,

Thank you.  Please try also customizing the option from the menu bar
and please also try its main feature: Make the frame sufficently
narrow, type M-x dired RET RET, and test whether the menu bar gets
truncated instead of resizing the frame.

>  and am seeing some minor display glitches
> from emacs -Q. The space allocated for the menu bar seems slightly too
> small, resulting in a dotted line underneath it, see screenshot. This
> is with gtk 3.22.30.

From that screenshot it's also evident that descenders are truncated,
in particular the "p" in Options, Help ...

martin