046234b3eb
don't expect drivers to be able to accelerate without exa assistance).
Instead, drop back to plain old miGlyphs for a 62.5% +/- 1.5% reduction
in runtime of my ls -lR test (n=5) with component alpha. While a
reasonable approach would seem to be making a better test to see
whether the entire path would be accelerated and force migration
appropriately, my attempt at this made the situation much worse.