make sure 64bit output is correct

test/stdio/64bit.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int main(void)
+{
+	void *ptr = (void *)-1;
+	printf("%p\n", ptr);
+	return 0;
+}

test/stdio/Makefile

@@ -0,0 +1,6 @@
+# uClibc assert tests
+# Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+
+include ../Test.mak
+
+DODIFF_64bit := 1