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ICU-13358 Fixed cpyscan problems. Enhanced cpyscan.pl to use online version of cpyskip.txt by default. Added the new Unicode copyright comment in many tools files.
ICU-21833 Replace UChar with char16_t in all C++ code.
ICU-7144 quick & dirty tool to recreate the UTS #46 data table according to the spec
ICU-7144 derive the base exclusion set by comparing IDNA2003 with NFKC_Casefold (follow change in UTS #46)