1.28.3 Character class: initializing lookup tables
- Initialize the lookup table which is used to make case and digit-to-char
Indices in Table are ASCII values incremented by one. Indices 1-256
classify chars (0 = nothing special, 2 = separator, 48 = digit,
55 = uppercase, 3 = lowercase), indices 257-512 map to lowercase chars,
indices 513-768 map to uppercase chars.