test: use 'stty size' for vtest --- line instead of 'tput cols'

vlib/term/can_show_color.v

@@ -27,3 +27,17 @@ pub fn fail_message(s string) string {
 	return if can_show_color_on_stdout() { red(s) } else { s }
 }
 
+// h_divider will return a horizontal divider line with a dynamic width,
+// that depends on the current terminal settings
+pub fn h_divider() string {
+	mut cols := 76
+	if term_size := os.exec('stty size') {
+		if term_size.exit_code == 0 {
+			term_cols := term_size.output.split(' ')[1].int()
+			if term_cols > 0 {
+				cols = term_cols
+      }
+		}
+	}
+	return '-'.repeat(cols)
+}  

vlib/term/control.v

@@ -95,4 +95,3 @@ pub fn show_cursor() {
 pub fn hide_cursor() {
 	print('\x1b[?25l')
 }
-