Fix antialias face attribute when text is scaled

Fix antialias face attribute when text is scaled

This restores the code we had in realize_gui_face before commit bf0d3f7.
The problem described in bug#17973, which led to that commit, only
happens if one uses a specific (misc-fixed) font family, not for
the usual default fonts used by Emacs, and I'm not sure what's
described there is a bug at all.  At least for the purposes of
text-scale-adjust, it makes no sense to ignore the
foundry/family/adstyle of the original font, because we _want_ the
same (or very similar) font, just of a different size.

And likely in other use cases: if the :font attribute of a face
specifies some font properties, we want to keep them all, not
arbitrarily to ignore some of them.  And definitely catering to an
obscure use case such as the one cited in bug#17973 is NOT a good
reason to make such radical changes in face-realization behavior.

So I think backing out that part of commit bf0d3f7 is TRT, and if
we decide that this causes bug#17973 in too many situations we care
about, I'd rather find a kludge for that specific case than do that
for every face realization.
* src/xfaces.c (realize_gui_face): Preserve face attributes when
text is scaled.  This reverts part of the changes installed in
commit bf0d3f7.  (Bug#37473)