cross-plat: fix build error after merge
cross-plat: fix build error after merge

Continue to have `wchar_t` defined to `char16_t` in PAL in
PAL_STDCPP_COMPAT mode.

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