input (curses): mask keycodes to remove modifier bits Without the mask, control bits are passed on in the keycode, generating incorrect PS/2 sequences when SHIFT, ALT, etc are held down. Cc: qemu-stable@nongnu.org Signed-off-by: Andrew Oates <andrew@aoates.org> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>