Add missing license header

Author: benesch

src/sqlast/ddl.rs

@@ -1,3 +1,15 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 //! AST types specific to CREATE/ALTER variants of `SQLStatement`
 //! (commonly referred to as Data Definition Language, or DDL)
 use super::{ASTNode, SQLIdent, SQLObjectName, SQLType};