-// FIXME There are still problems here with nesting, at least
-// potentially. The problem is that true nesting of text mode isn't
-// actually possible. I.e., we can't have:
-// <mtext><mtext></mtext></mtext>
-// So we have to have:
-// <mtext></mtext><mtext></mtext><mtext></mtext>
-// instead, where the last is really a continuation of the first.
-// We'll need some kind of stack to remember all that.