deal with XML in l10n_zh

[opoudjis]

Because of metanorma/isodoc#617, we are now putting XML markup in xrefs in Japanese. l10n needs to convert Latin punctuation into full-width punctuation, sensitive to context, but ignoring XML tags

So:

• In 箇条1)のa) , the parentheses are correctly being left half-width, because they are next to Latin text
• But we now have 箇条<semx>1</semx><span>)</span><semx>の</semx>a<span>)</span>. Currently that is being by node.traverse. That means that the <span>)</span> is being processed without access to its context outside the span, and as a result, it is always being converted to fullwidth.

To fix this, we need to pass the preceding and following text nodes in to the traverse loop.

[opoudjis]

Implemented, now tidying

[opoudjis]

generalised to French localisation of punct