(Face Functions): Mention face aliases.

lispref/display.texi

@@ -2523,6 +2523,17 @@ This returns non-@code{nil} if the face @var{face} displays
 differently from the default face.
 @end defun
 
+@cindex face alias
+A @dfn{face alias} provides an equivalent name for a face.  You can
+define a face alias by giving the alias symbol the @code{face-alias}
+property, with a value of the target face name.  The following example
+makes @code{modeline} an alias for the @code{mode-line} face.
+
+@example
+(put 'modeline 'face-alias 'mode-line)
+@end example
+
+
 @node Auto Faces
 @subsection Automatic Face Assignment
 @cindex automatic face assignment