Use raw arrays for uppercase/lowercase

[Alexey-T]

Uppercase/lowercase funcs in regex must be very fast. PUCU gives not fast funcs. (some [] indexes, etc). so engine could make internal arrays for first 0xFFFF chars like array[word] of word; they have big size but fast.

[benibela]

It is also not fully correct. E.g. K (U+212a) should match K or k case insensitively

But table lookups can be rather slow on modern systems when the table is not in the cache