And get rid of the constraining FX() macro, with its spacing parameter
that we haven't even seen used so far.
Part of P0124, funded by [Anonymous] and Blue Bolt.
I did consider not doing this, because "well, can't anyone who's
*actually* interested just diff the TH01 and TH02 implementations to
figure out the differences themselves", but that duplication ended up
feeling too filthy after all.
And hey, it's a nice excuse to update TH02's version to current naming
standards! 😛
Part of P0068, funded by Yanga.