Make String move constructor move instead of copy.

The move constructor String::String(String&&) and String::operator=(String&&)
now perform move instead of copy.

Remove String(StringSumHelper&&) constructor because having it makes no sense:
String(String&&) takes care of it - you can pass either String&& or
StringSumHelper&& to this constructor. StringSumHelper is derived from String
and has no data members other than those inherited from String. Even if it did
have some extra data members, truncation would have to happen during move, and
normally that is something you don't want.

Author: leg0

api/String.cpp

@@ -63,18 +63,15 @@ String::String(const __FlashStringHelper *pstr)
 	*this = pstr;
 }
 
-#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String::String(String &&rval)
+	: buffer(rval.buffer)
+	, capacity(rval.capacity)
+	, len(rval.len)
 {
-	init();
-	move(rval);
+	rval.buffer = NULL;
+	rval.capacity = 0;
+	rval.len = 0;
 }
-String::String(StringSumHelper &&rval)
-{
-	init();
-	move(rval);
-}
-#endif
 
 String::String(char c)
 {
@@ -214,28 +211,21 @@ String & String::copy(const __FlashStringHelper *pstr, unsigned int length)
 	return *this;
 }
 
-#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 void String::move(String &rhs)
 {
-	if (buffer) {
-		if (rhs && capacity >= rhs.len) {
-			memcpy(buffer, rhs.buffer, rhs.len);
-			len = rhs.len;
-			buffer[len] = '\0';
-			rhs.len = 0;
-			return;
-		} else {
-			free(buffer);
-		}
+	if (this != &rhs)
+	{
+		free(buffer);
+
+		buffer = rhs.buffer;
+		len = rhs.len;
+		capacity = rhs.capacity;
+
+		rhs.buffer = NULL;
+		rhs.len = 0;
+		rhs.capacity = 0;
 	}
-	buffer = rhs.buffer;
-	capacity = rhs.capacity;
-	len = rhs.len;
-	rhs.buffer = NULL;
-	rhs.capacity = 0;
-	rhs.len = 0;
 }
-#endif
 
 String & String::operator = (const String &rhs)
 {
@@ -247,19 +237,11 @@ String & String::operator = (const String &rhs)
 	return *this;
 }
 
-#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String & String::operator = (String &&rval)
 {
-	if (this != &rval) move(rval);
-	return *this;
-}
-
-String & String::operator = (StringSumHelper &&rval)
-{
-	if (this != &rval) move(rval);
+	move(rval);
 	return *this;
 }
-#endif
 
 String & String::operator = (const char *cstr)
 {

api/String.h

@@ -72,10 +72,7 @@ class String
 	String(const uint8_t *cstr, unsigned int length) : String((const char*)cstr, length) {}
 	String(const String &str);
 	String(const __FlashStringHelper *str);
-	#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String(String &&rval);
-	String(StringSumHelper &&rval);
-	#endif
 	explicit String(char c);
 	explicit String(unsigned char, unsigned char base=10);
 	explicit String(int, unsigned char base=10);
@@ -99,10 +96,7 @@ class String
 	String & operator = (const String &rhs);
 	String & operator = (const char *cstr);
 	String & operator = (const __FlashStringHelper *str);
-	#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String & operator = (String &&rval);
-	String & operator = (StringSumHelper &&rval);
-	#endif
 
 	// concatenate (works w/ built-in types)
 
@@ -233,9 +227,7 @@ class String
 	// copy and move
 	String & copy(const char *cstr, unsigned int length);
 	String & copy(const __FlashStringHelper *pstr, unsigned int length);
-	#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	void move(String &rhs);
-	#endif
 };
 
 class StringSumHelper : public String