Fixed problem with ansi mode and GROUP BY with constants. (Bug #387)

sql/sql_select.cc:
  Fixed problem with ansi mode and GROUP BY with constants

mysql-test/r/ansi.result

+drop table if exists t1;
+SELECT 'A' || 'B';
+'A' || 'B'
+AB
+CREATE TABLE t1 (id INT, id2 int);
+SELECT id,NULL,1,1.1,'a' FROM t1 GROUP BY id;
+id	NULL	1	1.1	a
+SELECT id FROM t1 GROUP BY id2;
+'t1.id' isn't in GROUP BY
+drop table t1;

mysql-test/t/ansi-master.opt

+--ansi

mysql-test/t/ansi.test

+#
+# Test of ansi mode
+#
+
+drop table if exists t1;
+
+# Test some functions that works different in ansi mode
+
+SELECT 'A' || 'B';
+
+# Test GROUP BY behaviour
+
+CREATE TABLE t1 (id INT, id2 int);
+SELECT id,NULL,1,1.1,'a' FROM t1 GROUP BY id;
+--error 1055
+SELECT id FROM t1 GROUP BY id2;
+drop table t1;

sql/sql_select.cc

@@ -6668,7 +6668,8 @@ setup_group(THD *thd,TABLE_LIST *tables,List<Item> &fields,
 
     while ((item=li++))
     {
-      if (item->type() != Item::SUM_FUNC_ITEM && !item->marker)
+      if (item->type() != Item::SUM_FUNC_ITEM && !item->marker &&
+	  !item->const_item())
       {
 	my_printf_error(ER_WRONG_FIELD_WITH_GROUP,
 			ER(ER_WRONG_FIELD_WITH_GROUP),