add the missing code file for the db flush

ledis/ledis_db.go

@@ -0,0 +1,19 @@
+package ledis
+
+func (db *DB) Flush() (drop int64, err error) {
+	all := [...](func() (int64, error)){
+		db.KvFlush,
+		db.LFlush,
+		db.HFlush,
+		db.ZFlush}
+
+	for _, flush := range all {
+		if n, e := flush(); e != nil {
+			err = e
+			return
+		} else {
+			drop += n
+		}
+	}
+	return
+}