[ZPT] Strange behavior of METAL

[Denis S. Otkidach]

Here is a typical example of MATAL usage:
== macro definition ==
<div metal:define-macro="twocolumn">
<table>
  <tr>
    <td><div metal:define-slot="column1">Column1</div></td>
    <td><div metal:define-slot="column2">Column2</div></td>
  </tr>
</table>
</div>
== end ==

== macro usage ==
<div metal:use-macro="macros/twocolumn">
<div tal:omit-tag="" metal:fill-slot="column1">The text in 1st
column</div>
<div tal:omit-tag="" metal:fill-slot="column2">The text in 2nd
column</div>
</div>
== end ==

The "metal:fill-slot" has no sense without "tal:omit-tag", since in that
case we rely on internal structure of macro (its surounding tag of
slot). Furthermore the <div> tag in macro definition seems to be
reduntant.