riched20: Use \ulnone instead of \ul0 for no underline.

[Huw Davies]

On Mon, Aug 19, 2013 at 05:38:13PM -0500, Vincent Povirk wrote:
> Testing on Windows (by saving rtf documents with wordpad and viewing
> them with notepad) shows that it uses \ulnone instead of \ul0 to end
> underline. Wine and Windows are both able to read either one.

I think these are symonyms and indeed Windows seems to use \ulnone, so
this looks good to me.

Huw.