Replace binary search of ranges with trie lookup using leaves of
64-bit bitmap chunks. Benchmarks suggest this is approximately 10x
faster than the bsearch approach.

Somehow got in my head that >> 8 was the right shift for a chunk of 64.
Oops, sorry.

Adds a comment which explains the trie structure, and also does a
little arithmetic on lookup (no measurable impact, looks like modern
CPUs do this arithmetic in parallel with the memory lookup to find the
node) to save a bit of space. As a result, the memory impact of the
compiled tables is within a couple hundred bytes of the old
bsearch-range structure.