encoding: Rework encoding lookup Add missing xmlCharEncoding enum values. Simplify and speed up encoding lookup by using a table mapping names to xmlCharEncoding enums and binary search. Rearrange the default handler table to match the enum layout. For some encodings we now only lookup the provided or most canonical name instead of trying several names, expecting that iconv or ICU handle aliases: - IBM037 (EBCDIC) - UCS-2 - UCS-4 - Shift_JIS