PR #336: since we can't use function overriding (due to problems with it on

OSX) always include the _json_c_strerror function but only enable it with a flag
 during tests.

tests/test_json_pointer.c

@@ -1,4 +1,5 @@
 #include "strerror_override.h"
+#include "strerror_override_private.h"
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>
@@ -280,6 +281,8 @@ static void test_wrong_inputs_set()
 
 int main(int argc, char **argv)
 {
+	_json_c_strerror_enable = 1;
+
 	test_example_get();
 	test_recursion_get();
 	test_wrong_inputs_get();