MBED_NO_GLOBAL_USING_DIRECTIVE is added to remove auto-addition of namespace

Macro guard `MBED_NO_GLOBAL_USING_DIRECTIVE` is added around namespace, to avoid
polluting users namespace.

Author: deepikabhavnani

events/mbed_events.h

@@ -30,7 +30,9 @@
 
 #include "events/mbed_shared_queues.h"
 
+#ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
 using namespace events;
+#endif
 
 #endif
 

mbed.h

@@ -102,7 +102,9 @@
 #include "platform/FunctionPointer.h"
 #include "platform/ScopedLock.h"
 
+#ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
 using namespace mbed;
 using namespace std;
+#endif
 
 #endif

rtos/Mail.h

@@ -33,7 +33,9 @@
 
 #include "platform/NonCopyable.h"
 
+#ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
 using namespace rtos;
+#endif
 
 namespace rtos {
 /** \addtogroup rtos */

rtos/rtos.h

@@ -38,7 +38,9 @@
 #include "rtos/EventFlags.h"
 #include "rtos/ConditionVariable.h"
 
+#ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
 using namespace rtos;
+#endif
 
 /* Get mbed lib version number, as RTOS depends on mbed lib features
    like mbed_error, Callback and others.