Improve gen-duck formatting.

src/duck-extract.scm

@@ -46,6 +46,8 @@
  (define (print-duck-module sec)
    (print "## " (cadr sec) " [module]")
    (newline)
+   (print "    (import " (cadr sec) ")")
+   (newline)
    (print-duck-text (caddr sec)))
 
  (define (print-duck-variable sec)

src/gendoc.scm

@@ -3,12 +3,14 @@
 
 (define-syntax gen-duck
   (syntax-rules ()
-    ((_ fname title mod ...)
+    ((_ fname title abstract mod ...)
      (begin
        (import mod ...)
        (with-output-to-file fname
 	 (lambda ()
 	   (print "# " title)
+	   (newline)
+	   (print abstract)
 	   (let ()
 	     (newline)
 	     (print-module-duck mod))
@@ -17,4 +19,5 @@
 
 (gen-duck "doc/d-utils.md"
 	  "Utility modules"
+	  "These are various utility modules for other HackerBase libraries."
 	  util-time)