Null-merge from mysql-5.5.7-rc-release.

Null-merging revision
'revid: kevin.lewis@oracle.com-20101102151655-b9oe4ii46szw7vx1'
(Bug_57904 - Only one INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS was displayed
per table from Innodb) from mysql-5.5.7-rc-release.

The patch is already in mysql-5.5.8-release
(revid: kevin.lewis@oracle.com-20101102150314-a3jx98sg7wm3emge).