Added include protection for unistd.h and sys/time.h.

diff --git a/windows/winhelp.c b/windows/winhelp.c
index e6123dd..0c46dfb 100644
--- a/windows/winhelp.c
+++ b/windows/winhelp.c
@@ -18,10 +18,14 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include "config.h"
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
-#include <unistd.h>
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
 #include "wine/debug.h"
 #include "windef.h"
 #include "wingdi.h"