Clean up all links in headline when linking to it

So far, we only considered one link in a headline and replaced it with its
description when linking to it.  When there are multiple links, this will fail.
This commit changes this by iterating over all links in the headline, not only
the first one.

site-lisp/db-org.el

@@ -738,7 +738,7 @@ link."
     ;; When item is a link, only use it's description when available; otherwise
     ;; use the link part
     (save-match-data
-      (when (string-match org-link-bracket-re item)
+      (while (string-match org-link-bracket-re item)
         (let ((desc (or (match-string-no-properties 2 item)
                         (match-string-no-properties 1 item))))
           (setq item (concat (substring item 0 (match-beginning 0))