[1.9>master] [1.8>1.9] [MERGE #4611 @obastemur] clang 6.0 support
[1.9>master] [1.8>1.9] [MERGE #4611 @obastemur] clang 6.0 support

Merge pull request #4611 from obastemur:clang_6_18

Fixes couple of tiny issues we had with upcoming clang 6.0 release

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