simplify Clear() in Window and its derivatives

it removes argument responsible for immediate refreshing.
since after all calls that were refreshing screen there was
call to Refresh() anyway, this switch doesn't make much sense.

src/scrollpad.cpp

@@ -181,7 +181,7 @@ void Scrollpad::Scroll(Where where)
 	}
 }
 
-void Scrollpad::Clear(bool clear_screen)
+void Scrollpad::Clear()
 {
 	itsRealHeight = itsHeight;
 	itsBuffer.Clear();
@@ -192,8 +192,6 @@ void Scrollpad::Clear(bool clear_screen)
 	SetColor(itsColor, itsBgColor);
 	ForgetFormatting();
 	keypad(itsWindow, 1);
-	if (clear_screen)
-		Refresh();
 }
 
 void Scrollpad::Reset()