* doc/lispref/strings.texi (Creating Strings): Document them. * lisp/faces.el: Don't require subr-x, because that leads to build errors. * lisp/subr.el (string-trim, string-trim-right) (string-trim-left): Move here from subr-x.el. * lisp/emacs-lisp/shortdoc.el (string): Adjust.