Fix reporter using part of the actual message as a format string

When not reporting via events, the final contents of the message buffer
after formatting was being used as a format string to fprintf instead of
writing out the actual string.

src/Reporter.cc

@@ -302,7 +302,7 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Conne
 		s += buffer;
 		s += "\n";
 
-		fprintf(out, s.c_str());
+		fprintf(out, "%s", s.c_str());
 		}
 
 	if ( alloced )