merge from 5.2

sql/sql_string.h

@@ -438,6 +438,7 @@ public:
     return FALSE;
   }
   void print(String *print);
+  void append_for_single_quote(const char *st, uint len);
 
   /* Swap two string objects. Efficient way to exchange data without memcpy. */
   void swap(String &s);