Merge pull request #917 from 0xc0170/fix_exit_retarget

Fix for #908, exit req std namespace

Author: 0xc0170

libraries/mbed/common/retarget.cpp

@@ -493,6 +493,7 @@ extern "C" void mbed_exit(int return_code) {
 #elif defined TOOLCHAIN_GCC_ARM
 extern "C" void _exit(int return_code) {
 #else
+namespace std {
 extern "C" void exit(int return_code) {
 #endif
 
@@ -513,6 +514,10 @@ extern "C" void exit(int return_code) {
     while (1);
 }
 
+#if !defined(TOOLCHAIN_GCC_ARM) && !defined(TOOLCHAIN_GCC_CW)
+} //namespace std
+#endif
+
 
 namespace mbed {