Define PRId64 and PRIu64 when missing.
Include config.h before using feature macros.  Include unistd.h for getopt()
diff --git a/regress/modify.c b/regress/modify.c
index b0bde06..7ceba9f 100644
--- a/regress/modify.c
+++ b/regress/modify.c
@@ -32,10 +32,14 @@
 */
 
 
+#include "config.h"
 
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 
 #ifndef HAVE_GETOPT
 #include "getopt.h"