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ICU-23364 Implement support for the new CLDR dayOfMonths resource in ICU, along with unit tests. This PR also includes a temporary version of the relevant CLDR data (to be overwritten by the next CLDR integration) and an update to the CLDR-to-ICU tool to account for the new resource.
ICU-12764 icu4c utf-8 source files, update Copyright notices.
ICU-23437 Lookahead colouring
ICU-23471 Fix sanitizer check for state minimization in rbbitblb.cpp
ICU-23056 headertest: use header-specific .cpp filename
ICU-23475 Move MessageFormat2 C++ test files
ICU-23151 Fixed pkgdata crash with Clang-CL
ICU-23132 Include the source files, not their copies
ICU-21580 change site.icu-project.org to icu.unicode.org etc
ICU-22721 Add missing const (-Wwritable-strings).
ICU-20652 Adds Makefile.in, a fuzzer driver, and minor changes to in fuzzer targets to test/fuzzer/ directory. This will enable compilation and smoke test of fuzzer targets as part of the ICU continuous build.