Make sure getopt is properly defined

Author: FilipeMaia

tests/AllTests.c

@@ -1,13 +1,14 @@
-#include "AllTests.h"
-
-#include <time.h>
 #if defined(_WIN32) || defined(WIN32)
 #include "getopt.h"
 #else
-#define _POSIX_C_SOURCE 2
+// For getopt
+#define _XOPEN_SOURCE 600
 #include <unistd.h>
 #endif
 
+#include <time.h>
+#include "AllTests.h"
+
 typedef struct {
 	int linear_alg;
 	int phasing;