qapi2texi: Plainer enum value and member name formatting

Use @code{%s} instead of @code{'%s'}.  Impact, using @id as example:

* Texinfo
  -@item @code{'id'}
  +@item @code{id}

* HTML
  -<dt><code>'id'</code></dt>
  +<dt><code>id</code></dt>

* POD (for manual pages):
  -=item C<'id'>
  +=item C<id>

* Formatted manual pages:
  -'id'
  +"id"

* Plain text:
  -     ''id''
  +     'id'

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1489582656-31133-21-git-send-email-armbru@redhat.com>

scripts/qapi2texi.py

@@ -130,12 +130,12 @@ def texi_body(doc):
 
 def texi_enum_value(value):
     """Format a table of members item for an enumeration value"""
-    return "@item @code{'%s'}\n" % value.name
+    return '@item @code{%s}\n' % value.name
 
 
 def texi_member(member):
     """Format a table of members item for an object type member"""
-    return "@item @code{'%s'}%s\n" % (
+    return '@item @code{%s}%s\n' % (
         member.name, ' (optional)' if member.optional else '')