ue4 fstring 和std::string互转

https://forums.unrealengine.com/development-discussion/c-gameplay-programming/6517-convert-std-string-to-fstring

Code:

FString UE4Str = "UE4 C++"; 

//FString to std::string
std::string cstr(TCHAR_TO_UTF8(*UE4Str));

//std::string to FString
ClientMessage(FString(cstr.c_str()));