Support custom normalization data, especially for the mappings/decompositions. This is useful for UTS !#46 (for IDNAbis), combining NFKC with case folding (new NFKC_Casefold property in Unicode 5.2) and other variations of "Unicode normalization except...".
#5072 add function for normalization + case folding
#7144 Support TR46 (IDNA Update)
#7202 Update StringPrep