StreamConstPtr: disallow passing a String temporary (esp8266#8410)

* StreamConstPtr: prevent from passing a temporary String instance
* unconditionally allow progmem chars
* missing virtual destructor in Stream
(warning: deleting object of abstract class type 'Stream' which has non-virtual destructor will cause undefined behavior [-Wdelete-non-virtual-dtor])

Author: d-a-v

Diff for: cores/esp8266/Stream.h

@@ -61,6 +61,7 @@ class Stream: public Print {
         virtual int peek() = 0;
 
         Stream() {}
+        virtual ~Stream() {}
 
 // parsing methods
 

Diff for: cores/esp8266/StreamDev.h

@@ -160,6 +160,7 @@ class StreamConstPtr: public StreamNull
     size_t _peekPointer = 0;
 
 public:
+    StreamConstPtr(const String&& string) = delete; // prevents passing String temporary, use ctor(buffer,size) if you know what you are doing
     StreamConstPtr(const String& string): _buffer(string.c_str()), _size(string.length()), _byteAddressable(true) { }
     StreamConstPtr(const char* buffer, size_t size): _buffer(buffer), _size(size), _byteAddressable(__byteAddressable(buffer)) { }
     StreamConstPtr(const uint8_t* buffer, size_t size): _buffer((const char*)buffer), _size(size), _byteAddressable(__byteAddressable(buffer)) { }

Diff for: cores/esp8266/StreamSend.cpp

@@ -341,7 +341,7 @@ Stream& operator << (Stream& out, Stream& stream)
 
 Stream& operator << (Stream& out, const char* text)
 {
-    StreamConstPtr(text).sendAll(out);
+    StreamConstPtr(text, strlen_P(text)).sendAll(out);
     return out;
 }