converters/utf8proc: Update to 2.2.0

Changes:
- Unicode 11 support
- utf8proc_NFKC_Casefold convenience function for NFKC_Casefold
  normalization
- UTF8PROC_STRIPNA option to strip unassigned codepoints.
- Support building static libraries on Windows (callers need to
  #define UTF8PROC_STATIC)
- cmake fix to avoid defining UTF8PROC_EXPORTS globally
- toupper of U+00df now yields U+1E9E, similar to musl; case-folding
  still yields the standard "ss" mapping.
- utf8proc_charwidth now returns 1 for U+00AD (soft hyphen) and for
  unassigned/PUA codepoints.

(minskim)