Improve support for min-colors req in `defface'. lisp/faces.el (face-spec-set-match-display): Protect against `display-color-cells' returning nil. Delete unreferenced let-binding of `min-colors'. man/lispref/customize.texi (Face Definitions): New node. (Customization): Add entry to menu. (Variable Definitions): Add cross-ref for `defface'. (Customization Types): Fixup Previous link. man/lispref/faces.texi (Faces): Clarify that built-in properties of faces are computed at runtime.