Fix "uvuni_to_utf8(): deprecated function being removed from Perl #50"

[Copilot]

Fixes #50 by replacing the deprecated uvuni_to_utf8() function with uvchr_to_utf8().

Problem

The uvuni_to_utf8() function has been deprecated since Perl 5.32 and is now being removed from Perl blead, causing build failures for HTML::Parser. The function was used in util.c for converting Unicode code points to UTF-8 byte sequences when decoding HTML entities.

Solution

Replace the single occurrence of uvuni_to_utf8() with uvchr_to_utf8() in util.c. Both functions have identical signatures and behavior:

// Before (deprecated)
tmp = (char*)uvuni_to_utf8((U8*)buf, num);

// After (current)
tmp = (char*)uvchr_to_utf8((U8*)buf, num);

Testing

• All existing tests continue to pass (464 tests)
• Manual verification confirms Unicode entity decoding works correctly for:
  • Basic ASCII characters (A → A)
  • Extended Latin characters (é → é)
  • Unicode BMP characters (☺ → ☺)
  • Unicode supplementary plane characters (😀 → 😀)

This is a minimal, surgical fix that maintains full backward compatibility while ensuring the module continues to build on modern Perl versions.

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