Prevent unexpected }- in converter output

Prevent unexpected }- in converter output

Previously for input -{<span title="-{X}-">X</span>}-, the converter
sees -{<span title="-&#123;X}-">A</span>}-, so <span title="-&#123;X
becomes the content in the first block, and a stray }- is left to output.

Now, the converter sees -{<span title="-&#123;X&#125;-">A</span>}- with
this change. In further processing, the span tag may be parsed and have
its title attrib converted. For cases where the content is not processed
further (eg. "R" = raw flag), "-{X}-" is left as is in the attrib, which
is not so ideal, but at least it's better than the original extra }-
outside the whole tag.

Change-Id: Idbaaf53f914f362e5b8cc9fad02a524f8d591bb7