scribble: fix 'aux stripping for hyperlinks and HTML titles

original commit: ce960756cbea2fa1bafdc0497bb558af851596f6

collects/scribble/core.rkt

@@ -619,14 +619,24 @@
 (define (aux-element? e)
   (and (element? e)
        (let ([s (element-style e)])
-         (and (style? e)
+         (and (style? s)
               (memq 'aux (style-properties s))))))
 
 (define (strip-aux content)
   (cond
     [(null? content) null]
     [(aux-element? content) null]
-    [(list? content) (map strip-aux content)]
+    [(element? content)
+     (define c (element-content content))
+     (define p (strip-aux c))
+     (if (equal? c p)
+         content
+         (struct-copy element content [content p]))]
+    [(list? content) 
+     (define p (map strip-aux content))
+     (if (equal? p content)
+         content
+         p)]
     [else content]))
 
 ;; ----------------------------------------

collects/scribble/html-render.rkt

@@ -667,7 +667,7 @@
                [title (cond [(part-title-content d)
                              => (lambda (c)
                                   `(title ,@(format-number number '(nbsp))
-                                          ,(content->string c this d ri)))]
+                                          ,(content->string (strip-aux c) this d ri)))]
                             [else `(title)])])
           (unless (bytes? style-file)
             (unless (lookup-path style-file alt-paths)