bug#7881: 23.2.91; Bold spaces sometimes(?) underlined in man pages

[Chong Yidong]

Glenn Morris <rgm@gnu.org> writes:

> Andreas Schwab wrote:
>
>>> where the space between “include” and “<stdlib.h>” is shown underlined.
>>
>> That's because it's a button, and the button face is underlined.
>
> Why isn't the whole button underlined, just the space in the middle?
>
> Why don't the "see also" links at the end of the very same page have
> any visible underlining?
>
> Answering myself: because the links are made with `make-text-button',
> and it seems since it adds the button face as a text property, it
> loses out to any existing text properties (bold in this case).
>
> This seems a bit poor, doesn't it?
>
> `make-button', using overlays, doesn't suffer from this.

I think `make-button' is indeed the apropriate choice here, since the
button face needs to coexist with the other face text properties applied
by man.el.  Committed to trunk.