docs/parse-support-md: Unify identical [*] in footnotes

docs/parse-support-md: Unify identical [*] in footnotes

A section in the SUPPORT.md may mention multiple
   Status, something: Supported
and then have some text.  The text is linked to from [*] footnotes
in the table.  But, this means that each bit of text needs to
apply to multiple rows.

Before this commit this was a separate [*] after each applicable item.
But multiple apparently-different links to the same thing are annoying
for the reader.

So, in this commit we combine them.  Formatting the result is not
entirely trivial.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
---
v3: New patch
v3.1: Drop `}' in multi-row [*] notes.  I put this in to help work
   around firefox bugs eg
     https://bugzilla.mozilla.org/show_bug.cgi?id=244135
   but I have been convinced it is not generally wanted.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>