Stage 3 foundation of the faithful libyaml scanner port. Translates the IS_* character-class macros from yaml_private.h (IS_Z, IS_SPACE, IS_TAB, IS_BLANK, IS_BREAK, IS_BREAKZ, IS_SPACEZ, IS_BLANKZ, IS_DIGIT, IS_ALPHA, IS_HEX, IS_ASCII, IS_PRINTABLE) into PureYAML.Parsing.LibYAML.CharacterClass. libyaml inspects UTF-8 bytes; the Swift port operates on Unicode.Scalar, where the multi-byte line breaks NEL (U+0085), LS (U+2028), and PS (U+2029) are single scalars, and end of input is nil, libyaml's \0 sentinel (so isZ(nil) is true and the others are false). These predicates are what the token fetchers dispatch on. Unit-tested for end-of-input, blanks, the full break set, the alpha/digit/hex sets, and the ascii/printable boundaries.
Mihaela Mihaljevic
348af8b77b