Close the two XSD-regex gaps from the audit:
- \p{...} and \P{...} now resolve Unicode general categories (one-letter
groups like \p{L} and two-letter codes like \p{Lu}/\p{Nd}) through
Swift's own scalar generalCategory, so no character tables are vendored.
A curated set of well-known \p{Is<Block>} blocks is supported; an
unknown category or block name is a compile error rather than a guess.
- Character-class subtraction [a-z-[aeiou]] removes the subtrahend from a
class, and nests ([a-z-[b-d-[c]]]) and composes with categories.
Categories and subtraction work both as standalone atoms and inside
character classes, so XSD pattern facets that use them now validate.
Closes#89
Mihaela Mihaljevic
f5c04058dc