message: Documentation reference tidy
diff: <member><link linkend="beast.ref.http__serializer">serializer</link></member>
  <member><link linkend="beast.ref.http__string_body">string_body</link></member>
  </simplelist>
  + <bridgehead renderas="sect3">rfc7230</bridgehead>
  + <simplelist type="vert" columns="1">
  + <member><link linkend="beast.ref.http__ext_list">ext_list</link></member>
  + <member><link linkend="beast.ref.http__opt_token_list">opt_token_list</link></member>
  + <member><link linkend="beast.ref.http__param_list">param_list</link></member>
  + <member><link linkend="beast.ref.http__token_list">token_list</link></member>
  + </simplelist>
  </entry>
  <entry valign="top">
  <bridgehead renderas="sect3">Functions</bridgehead>
  </simplelist>
  </entry>
  <entry valign="top">
  - <bridgehead renderas="sect3">rfc7230</bridgehead>
  - <simplelist type="vert" columns="1">
  - <member><link linkend="beast.ref.http__ext_list">ext_list</link></member>
  - <member><link linkend="beast.ref.http__opt_token_list">opt_token_list</link></member>
  - <member><link linkend="beast.ref.http__param_list">param_list</link></member>
  - <member><link linkend="beast.ref.http__token_list">token_list</link></member>
  - </simplelist>
  <bridgehead renderas="sect3">Constants</bridgehead>
  <simplelist type="vert" columns="1">
  <member><link linkend="beast.ref.http__connection">connection</link></member>
  