Goodness, that was brutal.

The `!-` name doesn't work as a title for the conversion from ReST to
Markdown.  Maybe that's a bug in Pandoc, but more likely it's a legit
syntax gotcha in Mearkdown itself.

    !-
    ^^^^

In ReST turns into:

    !-\^\^\^\^

In the Markdown.  :(

It should be:

    # !-

Instead.

docs/reference/Makefile

@@ -1,4 +1,4 @@
-NOT_US = Functor-Reference.md FORMAT-Functor-Reference.md
+NOT_US = Functor-Reference.md FORMAT-Functor-Reference.md HEADER.md
 FUNCDOCS = $(filter-out $(NOT_US),$(wildcard *.md))