Moved Stream.flush() to Print.flush()

Author: cmaglie

Diff for: api/Print.h

@@ -82,5 +82,7 @@ class Print
     size_t println(double, int = 2);
     size_t println(const Printable&);
     size_t println(void);
+
+    virtual void flush() { /* Empty implementation for backward compatibility */ }
 };
 

Diff for: api/Stream.h

@@ -58,7 +58,6 @@ class Stream : public Print
     virtual int available() = 0;
     virtual int read() = 0;
     virtual int peek() = 0;
-    virtual void flush() = 0;
 
     Stream() {_timeout=1000;}