Fix Bug#21704 Renaming column does not update FK definition

by checking whether a column that participates in a FK definition is being
renamed and denying the ALTER in this case.

The patch was originally developed by Davi Arnaut <Davi.Arnaut@Sun.COM>:
http://lists.mysql.com/commits/77714
and was later adjusted to conform to InnoDB coding style by me (Vasil),
I also added some more comments and moved the bug specific mysql-test to
a separate file to make it more manageable and flexible.