add StreamString class (implement the Stream interface for String)

cores/esp8266/StreamString.h

@@ -0,0 +1,40 @@
+/**
+ StreamString.h
+
+ Copyright (c) 2015 Markus Sattler. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+#ifndef STREAMSTRING_H_
+#define STREAMSTRING_H_
+
+
+class StreamString: public Stream, public String {
+
+        size_t write(const uint8_t *buffer, size_t size);
+        size_t write(uint8_t data);
+
+        int available();
+        int read();
+        int peek();
+        void flush();
+
+};
+
+
+#endif /* STREAMSTRING_H_ */