patch 9.0.0787: mouse scrolling in terminal misbehaves without dll

Problem:    MS-Windows: mouse scrolling in terminal misbehaves without dll.
Solution:   Add #ifdef as a temporary solution. (Christopher Plewright,
            closes #11392)
diff --git a/src/os_win32.c b/src/os_win32.c
index 003fdea..db43c9e 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -1397,14 +1397,14 @@
     // unprocessed mouse click?
     if (g_nMouseClick != -1)
 	return TRUE;
-
+#ifdef VIMDLL
     if (pmer->dwEventFlags == MOUSE_WHEELED
 				       || pmer->dwEventFlags == MOUSE_HWHEELED)
     {
 	decode_mouse_wheel(pmer);
 	return TRUE;  // we now should have a mouse scroll in g_nMouseClick
     }
-
+#endif
     nButton = -1;
     g_xMouse = pmer->dwMousePosition.X;
     g_yMouse = pmer->dwMousePosition.Y;