Compile for either C++11 or C++0x

teensy3/WString.cpp

 	*this = value;
 }
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String::String(String &&rval)
 {
 	init();
 	return copy(rhs.buffer, rhs.len);
 }
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String & String::operator = (String &&rval)
 {
 	if (this != &rval) move(rval);

teensy3/WString.h

 	String(const char *cstr = (const char *)NULL);
 	String(const __FlashStringHelper *pgmstr);
 	String(const String &str);
-	#ifdef __GXX_EXPERIMENTAL_CXX0X__
+	#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String(String &&rval);
 	String(StringSumHelper &&rval);
 	#endif
 	String & operator = (const String &rhs);
 	String & operator = (const char *cstr);
 	String & operator = (const __FlashStringHelper *pgmstr);
-	#ifdef __GXX_EXPERIMENTAL_CXX0X__
+	#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String & operator = (String &&rval);
 	String & operator = (StringSumHelper &&rval);
 	#endif