Fixes for defcustoms, prompted by cus-test-opts

* lisp/files.el (save-some-buffers-default-predicate):
* lisp/time.el (display-time-world-list):
* lisp/gnus/gnus-art.el (gnus-article-show-cursor):
* lisp/progmodes/cc-vars.el (c-noise-macro-with-parens-names):
* lisp/progmodes/verilog-mode.el (verilog-auto-wire-type):
* lisp/textmodes/less-css-mode.el (less-css-output-directory)
(less-css-output-file-name, less-css-input-file-name):
* lisp/vc/emerge.el (emerge-metachars):
* lisp/vc/vc-hg.el (vc-hg-symbolic-revision-styles):
Fix :types.
* lisp/net/newst-backend.el (newsticker-url-list-defaults): Fix url.

lisp/textmodes/less-css-mode.el

@@ -106,7 +106,7 @@ Use \"-x\" to minify output."
 This path is expanded relative to the directory of the Less file
 using `expand-file-name', so both relative and absolute paths
 will work as expected."
-  :type 'directory)
+  :type '(choice (const :tag "Same as Less file" nil) directory))
 ;;;###autoload
 (put 'less-css-output-directory 'safe-local-variable 'stringp)
 
@@ -116,7 +116,7 @@ This can be also be set to a full path, or a relative path.  If
 the path is relative, it will be relative to the value of
 `less-css-output-dir', if set, or the current directory by
 default."
-  :type 'file)
+  :type '(choice (const :tag "Default" nil) file))
 (make-variable-buffer-local 'less-css-output-file-name)
 
 (defcustom less-css-input-file-name nil
@@ -132,7 +132,7 @@ variables.
 This can be also be set to a full path, or a relative path.  If
 the path is relative, it will be relative to the current
 directory by default."
-  :type 'file)
+  :type '(choice (const nil) file))
 ;;;###autoload
 (put 'less-css-input-file-name 'safe-local-variable 'stringp)
 (make-variable-buffer-local 'less-css-input-file-name)