[Debug] don't append new line to log message

Let the user of emper_log decide if they want a newline (most LOGX macros
do expect WDBG).

Currently since most LOGX macros append a new line to the log message
and emper_log adds one unconditionally we end up with an unnecessary
empty line per log message.

emper/Debug.cpp

@@ -55,7 +55,7 @@ void emper_log(const std::string& prefix, const std::string& message) {
 	logMessage << message;
 
 	std::unique_lock<std::mutex> lock(emper_log_mutex);
-	std::cerr << logMessage.str() << std::endl;
+	std::cerr << logMessage.str();
 }
 
 // global log_level which can be changed to control the log output