Fix panic on winsize syscall

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

pkg/term/term.go

@@ -27,6 +27,8 @@ type State struct {
 type Winsize struct {
 	Height uint16
 	Width  uint16
+	x      uint16
+	y      uint16
 }
 
 // StdStreams returns the standard streams (stdin, stdout, stedrr).