bug#46299: 28.0.50; Value of tab-bar-show not respected in new frames.

[martin rudalics]

> What if the user wants to manually enable the tab bar on one frame only
> without enabling tab-bar-mode?  Currently it's possible with
>
>    (add-hook 'after-make-frame-functions 'toggle-frame-tab-bar)

As a rule, this should be done by setting the 'tab-bar-lines' parameter
of that frame to non-zero, leaving it at zero for all other frames.

'toggle-frame-tab-bar' should stick to that rule.

martin