Register truncate function for DB2

Author: hazzik

src/NHibernate/Dialect/DB2Dialect.cs

@@ -132,6 +132,8 @@ public DB2Dialect()
 			RegisterFunction("length", new StandardSQLFunction("length", NHibernateUtil.Int32));
 			RegisterFunction("ltrim", new StandardSQLFunction("ltrim"));
 
+			RegisterFunction("truncate", new StandardSQLFunction("truncate"));
+
 			RegisterFunction("mod", new ModulusFunction(true, false));
 
 			RegisterFunction("substring", new StandardSQLFunction("substr", NHibernateUtil.String));