(Partially mined from an earlier issue regarding Windows launcher error messages)

DLL_ERROR4 is a macro expanding to an error message when a failure to load a generic item (shared libraries or an exported symbol from said libraries for example) occurs. "Error: loading:" is not a very pretty message, so this small change results in "Error: Failed to load %s" instead, which looks better and also means the message makes more sense if we want to append a reason behind as well, such as "Error: Failed to load libjvm.so because xxx"