-which causes display of the face FACE to use REPLACEMENT... instead.
-REPLACEMENT... is interpreted the same way as the value of a `face'
-text property: it may be (1) A face name, (2) A list of face names,
-(3) A property-list of face attribute/value pairs, or (4) A list of
-face names or lists containing face attribute/value pairs.
+ (1) a face name
+ (2) a property list of attribute/value pairs, or
+ (3) a list in which each element has the form of (1) or (2).