LP:1014750 - InnoDB weird Forgein Key Name handling

The followring DML is always processed right by Percona-XtraDB

ALTER TABLE `t1` ADD CONSTRAINT FOREIGN KEY (`col1`) REFERENCES `t2` (`col1`),
  ADD CONSTRAINT FOREIGN KEY (`col2`) REFERENCES `t3` (`col1`),
  ADD CONSTRAINT FOREIGN KEY (`col3`) REFERENCES `t4` (`col1`);

The same behaviour could be reproduced using a DDL.

But this engine becomes very strange when i like to give the f-keys custom-names like fk_col1 and so on.
Sometimes it helps to remove the underscore sometimes it helps to rename the f-key and so on.

So after about 2 hours i messed up finding any pattern so by now no f-key has a custom-name.

I think some kind of stristr is running an the aliases