* fhandler.h (class fhandler_console): Add members `savebufsiz' and

`savebuf' to allow save/restore of screen.
        * fhandler_console.cc (fhandler_console::dup): Duplicate savebuf.
        (fhandler_console::fhandler_console): Initialize `savebufsiz' and
        `savebuf'.
        (fhandler_console::char_command): Add terminal capabilities
        "save screen content" = \E[?47h and "restore screen content" = \E[?47l.

winsup/cygwin/fhandler.h

@@ -630,6 +630,10 @@ private:
   /* saved cursor coordinates */
   int savex, savey;
 
+  /* saved screen */
+  COORD savebufsiz;
+  PCHAR_INFO savebuf;
+
   struct
     {
       short Top, Bottom;