bug#5105: 23.1; doc string of facemenu-set-face

[Stefan Monnier]

>> How 'bout the other way around: give me a reason to accept strings.
> You're the one claiming that there is a good (even _obvious_) reason not to.
> What's the reason, if it's so obvious?

I'm not here to give software engineering courses, sorry.
But if you want, we can start from the very simplest: choice implies
performance and conceptual costs, so unless it's justified by actual
needs it's bad.
So we're back to "why do you think we should also accept strings?".

> And what about faces?  Can a given face have two different names?  We have

No, but two faces can have the same name.
And there can even be a face which has a unique name and yet `intern'
does not return the corresponding face.


        Stefan