Silence some warnings due to casts between pointer and integers of
different size.

diff --git a/windows/win.c b/windows/win.c
index 19dc0e6..596449d 100644
--- a/windows/win.c
+++ b/windows/win.c
@@ -3084,7 +3084,7 @@
         {
             HDC hDC = GetDC(hWnd);
 
-            if (!SendMessageW( hWnd, WM_ERASEBKGND, (WPARAM16)hDC, 0 ))
+            if (!SendMessageW( hWnd, WM_ERASEBKGND, (WPARAM)hDC, 0 ))
                 wndPtr->flags |= WIN_NEEDS_ERASEBKGND;
 
             ReleaseDC( hWnd, hDC );