xml export relies on implicit database ordering

[BenLubar]

Here's a diff of the English XML export over a period of two days: https://gist.github.com/BenLubar/fa10d1e5f014381b95df

The problem is that the gloss words are only sorted by definition ID and place structure, but when there are multiple gloss words for a single place, the database's internal ordering is used.

Here is the relevant query: https://github.com/lojban/jbovlaste/blob/master/export/xml-export.html#L123-L130

I suggest adding , nlw.word, nlw.meaning to the end of the ORDER BY line.