bug#21112: 25; Patch: show minibuffer messages with a face

[Drew Adams <drew.adams@oracle.com>]

> this patch against the Git repository makes the minibuffer messages
> appear with the same face as the minibuffer prompt, to make them
> more visually distinguished from user input.

FWIW, I hope this does not get applied in general.

Currently, *users* have control over the faces used in message
echoes.  It should remain that way.  It is trivial for user code
to control the output appearance now.  Let's not mess this up.

In fact, we should not even apply a face by default to the prompt.
That was a step backward (misguided), IMHO.  If a user (or library)
wants something different (other than customizing the prompt face,
which still gives the same appearance to the whole prompt), then
s?he now needs to fiddle.

Shouldn't be necessary.  We should have just left things
unhighlighted by default, letting users themselves (again,
trivially) propertize the prompt string any way they want.

Doing the kind of thing suggested by this enhancement request
does not add a feature.  It takes away a feature.  We already,
everyone, have the ability to propertize messages in any way
we like.  If you want them all to have face `minibuffer-prompt'
then you can accomplish that trivially - for your own use.