don't pick up /usr/include/db.h

Index: src/test/regression-storage.c
--- src/test/regression-storage.c.orig
+++ src/test/regression-storage.c
@@ -58,7 +58,7 @@ struct calendar
 int vcalendar_init(struct calendar **cal, const char *vcalendar, const char *title);
 
 #if defined(HAVE_BDB)
-#include <db.h>
+#include <db4/db.h>
 
 int get_title(DB *dbp, const DBT *pkey, const DBT *pdata, DBT *skey);
 char *parse_vcalendar(const DBT *dbt);