`FC_NFKC_Closure` is not a binary property

[mathiasbynens]

FC_NFKC_Closure is a string property, not a binary property. That is, it maps each code point to a sequence of code points, rather than to a Yes/No value.

DerivedNormalizationProps.txt holds the data.

Reported by @anba in tc39/proposal-regexp-unicode-property-escapes#27.