Get rid of unused using namespace std;

Author: MyNameIsTrez

Source/Managers/ThreadMan.cpp

@@ -1,7 +1,5 @@
 #include "ThreadMan.h"
 
-using namespace std;
-
 using namespace RTE;
 
 ThreadMan::ThreadMan() {

Source/Menus/MultiplayerGameGUI.cpp

@@ -2,7 +2,6 @@
 
 #include "FrameMan.h"
 
-using namespace std;
 using namespace RTE;
 
 MultiplayerGameGUI::MultiplayerGameGUI() {