The only user is currently String::equals_ignoring_case, but LibRegex
will need to do the same case-folded comparison with UTF-32 data. As it
turns out, the comparison works with all Unicode view types without much
fuss.
We currently fully casefold the left- and right-hand sides to compare
two strings with case-insensitivity. Now, we casefold one code point at
a time, storing the result in a view for comparison, until we exhaust
both strings.
The Unicode spec defines much more complicated caseless matching
algorithms in its Collation spec. This implements the "basic" case
folding comparison.
Since AK can't refer to LibUnicode directly, the strategy here is that
if you need case transformations, you can link LibUnicode and receive
them. If you try to use either of these methods without linking it, then
you'll of course get a linker error (note we don't do any fallbacks to
e.g. ASCII case transformations). If you don't need these methods, you
don't have to link LibUnicode.
