Replace StringFromInt with std::to_string

Updated version of #47. Android should support to_string now that
we use a modern version of libc++ when building.

Source/Core/Core/HW/WiimoteReal/IOAndroid.h

@@ -6,6 +6,7 @@
 
 #ifdef ANDROID
 #include <jni.h>
+#include <string>
 
 #include "Common/StringUtil.h"
 #include "Core/HW/WiimoteReal/WiimoteReal.h"
@@ -17,7 +18,7 @@ class WiimoteAndroid final : public Wiimote
 public:
   WiimoteAndroid(int index);
   ~WiimoteAndroid() override;
-  std::string GetId() const override { return "Android " + StringFromInt(m_mayflash_index); }
+  std::string GetId() const override { return "Android " + std::to_string(m_mayflash_index); }
 protected:
   bool ConnectInternal() override;
   void DisconnectInternal() override;