Explicitly use db-5.0 and don't default to db sym link

ext/dba/config.m4

@@ -358,7 +358,7 @@ if test "$PHP_DB4" != "no"; then
       break
     fi
   done
-  PHP_DBA_DB_CHECK(4, db-4.8 db-4.7 db-4.6 db-4.5 db-4.4 db-4.3 db-4.2 db-4.1 db-4.0 db-4 db4 db, [(void)db_create((DB**)0, (DB_ENV*)0, 0)])
+  PHP_DBA_DB_CHECK(4, db-5.0 db-4.8 db-4.7 db-4.6 db-4.5 db-4.4 db-4.3 db-4.2 db-4.1 db-4.0 db-4 db4 db, [(void)db_create((DB**)0, (DB_ENV*)0, 0)])
 fi
 PHP_DBA_STD_RESULT(db4,Berkeley DB4)