Fix bug #3478: InnoDB's FOREIGN KEY tables treated table and database names as case-insensitive; RENAME TABLE t to T would hang in an endless loop if t had a foreign key constraint defined on it
dict0dict.c:
  Fix bug #3478: InnoDB's FOREIGN KEY tables treated table and database names as case-insensitive; RENAME TABLE t to T would hang in an endless loop if t had a foreign key constraint defined on it; fix also a hang that would occur if one tried in ALTER TABLE or RENAME TABLE to create a foreign key constraint name that collided with another existing name