bpo-28518: Start a transaction implicitly before a DML statement (#245)

Patch by Aviv Palivoda.
diff --git a/Modules/_sqlite/statement.h b/Modules/_sqlite/statement.h
index 6eef168..8db10f6 100644
--- a/Modules/_sqlite/statement.h
+++ b/Modules/_sqlite/statement.h
@@ -38,7 +38,7 @@
     sqlite3_stmt* st;
     PyObject* sql;
     int in_use;
-    int is_ddl;
+    int is_dml;
     PyObject* in_weakreflist; /* List of weak references */
 } pysqlite_Statement;