[1.6>master] [MERGE #3081 @Cellule] UTF8 decode index signedness
[1.6>master] [MERGE #3081 @Cellule] UTF8 decode index signedness

Merge pull request #3081 from Cellule:utf8_null

Do not convert index from unsigned to signed when null termination in DecodeUnitsIntoAndNullTerminate

Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore