compile fix gcc-6
https://bugs.gentoo.org/show_bug.cgi?id=594322
Signed-of-by: Peter Levin <plevine457@gmail.com> 
Signed-of-by: Joerg  Bornkessel <hd_brummy@gentoo.org> ( 2016/Sep/29 )
--- sudoku-0.3.5/sudoku.h.old	2016-09-25 17:47:23.689678251 -0400
+++ sudoku-0.3.5/sudoku.h	2016-09-25 17:47:29.014272651 -0400
@@ -23,6 +23,10 @@
 
 #include <vector>
 
+#ifdef USE_RAND
+#include <stdlib.h>
+#include <time.h>
+#endif // USE_RAND
 
 namespace Sudoku
 {
@@ -32,8 +36,6 @@
 
 
 #ifdef USE_RAND
-#include <stdlib.h>
-#include <time.h>
   /** Random number 0 .. max-1 */
   static unsigned int rand(unsigned int max)
   {
