Please sort XML tags reproducibly

Please sort the order in which the XML tags are emitted in a reproducible manner.

Case in point, I was just loading all my scores (last saved with 2.2.1) in 2.3.1 and saving them, then reviewing the .mscx diff, and I got quite some delta for some scores.

Inside a ChordList tag’s font subtag, the mag subtag is always first, but the following sym subtags seem to come in arbitrary, random order instead of sorted.

There’s also fonts and font styles. When first saving a score, I get «font face="foo"/»bar, on second save this is changed to «font face="foo"»«/font»bar. For texts, tags like font, i, etc. do not seem to behave like normal XML tags, but instead like some sort of toggle, anyway…