* fhandler.h (class dev_console): Add backspace_keycode member.

* fhandler_console.cc (fhandler_console::get_tty_stuff): Initialize
	backspace_keycode with CERASE.
	(fhandler_console::read): Return dev_state->backspace_keycode if the
	backspace key is pressed.
	(fhandler_console::char_command): Implement DECBKM escape sequence.

winsup/cygwin/fhandler.h

@@ -924,6 +924,7 @@ class dev_console
   bool iso_2022_G1;
   bool alternate_charset_active;
   bool metabit;
+  char backspace_keycode;
 
   char my_title_buf [TITLESIZE + 1];