[Therion] Custom label style for a custom point

[Tarquin Wilton-Jones]

> I looked at a similar thing a while ago.  You have probably found this thread https://www.mail-archive.com/therion@speleo.sk/msg07234.html

Yes, thanks for the pointer though, because it means I am not alone.

What makes me worry is that I have to modify Therion's own Metapost code
for something so fundamental, which brings with it the chance that I
might cause some breakage later when Therion gets updated.

That particular workaround is pretty cool though, and I would love for
it to become a standard feature for all labels, like:
point label -style 5 -text "foo"
That way, those of us who want to apply a different style to just a
handful of labels, could do so without breaking all the others (Stacho's
suggestion would have applied to all height labels at once, which is not
desired here).

> My theory is that most Therion point symbols are defined so that alignments plot incorrectly if they also have a rotation applied.

Quite likely, but for now I stick to the convention in my own symbols,
not because it is right, but because it is (more) consistent.