Avoid warnings about 'image-scaling-factor' in builds --without-x

* lisp/cus-start.el (standard): Exclude 'image-*' options if Emacs
was built without GUI support.  (Bug#76716)

lisp/cus-start.el

@@ -908,6 +908,8 @@ since it could result in memory overflow and make Emacs crash."
 		       (fboundp 'x-create-frame))
 		      ((string-match "tab-bar-" (symbol-name symbol))
 		       (fboundp 'x-create-frame))
+                      ((string-match "image-" (symbol-name symbol))
+                       (fboundp 'x-create-frame))
 		      ((equal "vertical-centering-font-regexp"
 			      (symbol-name symbol))
 		       ;; Any function from fontset.c will do.