Fix for bug #28652: MySQL (with-debug=full) asserts when alter table operations

Problem: we may create a deadlock committing changes in the mysql_alter_table() when 
LOCK_open is set. Moreover, "in some variants of the ALTER TABLE commit
happens earlier, outside of LOCK_open, in other later - inside. It's no good, a storage 
engine code that is called in between could expect a consistency - either there is a 
transaction or there is not".
Fix: move the commit to happen earlier and outside of the LOCK_open.

mysql-test/r/innodb_mysql.result

@@ -617,4 +617,12 @@ EXPLAIN SELECT COUNT(*) FROM t2 WHERE stat_id IN (1,3) AND acct_id=785;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	range	idx1,idx2	idx1	9	NULL	2	Using where; Using index
 DROP TABLE t1,t2;
+create table t1(a int) engine=innodb;
+alter table t1 comment '123';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) default NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='123'
+drop table t1;
 End of 5.0 tests

mysql-test/t/innodb_mysql.test

@@ -597,4 +597,12 @@ EXPLAIN SELECT COUNT(*) FROM t2 WHERE stat_id IN (1,3) AND acct_id=785;
 
 DROP TABLE t1,t2; 
 
+#
+# Bug #28652: assert when alter innodb table operation
+#
+create table t1(a int) engine=innodb;
+alter table t1 comment '123';
+show create table t1;
+drop table t1;
+
 --echo End of 5.0 tests

sql/sql_table.cc

@@ -3776,6 +3776,9 @@ view_err:
                             alter_info->keys_onoff);
     table->file->external_lock(thd, F_UNLCK);
     VOID(pthread_mutex_unlock(&LOCK_open));
+    error= ha_commit_stmt(thd);
+    if (ha_commit(thd))
+      error= 1;
   }
 
   thd->last_insert_id=next_insert_id;		// Needed for correct log
@@ -3946,16 +3949,6 @@ view_err:
       goto err;
     }
   }
-  /* The ALTER TABLE is always in its own transaction */
-  error = ha_commit_stmt(thd);
-  if (ha_commit(thd))
-    error=1;
-  if (error)
-  {
-    VOID(pthread_mutex_unlock(&LOCK_open));
-    broadcast_refresh();
-    goto err;
-  }
   thd->proc_info="end";
   if (mysql_bin_log.is_open())
   {
@@ -4165,8 +4158,12 @@ copy_data_between_tables(TABLE *from,TABLE *to,
   }
   to->file->extra(HA_EXTRA_NO_IGNORE_DUP_KEY);
 
-  ha_enable_transaction(thd,TRUE);
-
+  if (ha_enable_transaction(thd, TRUE))
+  {
+    error= 1;
+    goto err;
+  }
+  
   /*
     Ensure that the new table is saved properly to disk so that we
     can do a rename