Fix function prototypes in curses_underscore.3

Correct function prototype of wunderscore(3) and wunderend(3).

lib/libcurses/curses_underscore.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: curses_underscore.3,v 1.5 2008/04/30 13:10:51 martin Exp $
+.\"	$NetBSD: curses_underscore.3,v 1.6 2018/09/29 21:52:29 kamil Exp $
 .\" Copyright (c) 2002 The NetBSD Foundation, Inc.
 .\" All rights reserved.
 .\"
@@ -25,7 +25,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd October 13, 2002
+.Dd September 29, 2018
 .Dt CURSES_UNDERSCORE 3
 .Os
 .Sh NAME
@@ -44,9 +44,9 @@
 .Ft int
 .Fn underend void
 .Ft int
-.Fn wunderscore void
+.Fn wunderscore "WINDOW *"
 .Ft int
-.Fn wunderend void
+.Fn wunderend "WINDOW *"
 .Sh DESCRIPTION
 These functions manipulate the underscore attribute on
 .Dv stdscr