InnoDB requires a full table rebuild for foreign key changes.
It was not possible in compare_tables() to detect such changes.

On Heikkis proposal I added a new flag to the syntax parser
where foreign key definition changes are done. I test for
this flag in compare_tables() now.


mysql-test/r/innodb.result:
  Bug#18477 - MySQL/InnoDB Ignoring Foreign Keys in ALTER TABLE
  Fixed an old test result.
  Added the new test result.
mysql-test/t/innodb.test:
  Bug#18477 - MySQL/InnoDB Ignoring Foreign Keys in ALTER TABLE
  Added the new test case.
sql/sql_lex.h:
  Bug#18477 - MySQL/InnoDB Ignoring Foreign Keys in ALTER TABLE
  Added a flag for foreign key definition changes.
sql/sql_table.cc:
  Bug#18477 - MySQL/InnoDB Ignoring Foreign Keys in ALTER TABLE
  Check for foreign key definition changes in 
  compare_tables(). If present, a table rebuild is required.
sql/sql_yacc.yy:
  Bug#18477 - MySQL/InnoDB Ignoring Foreign Keys in ALTER TABLE
  Marked foreign key definitions with the new flag.
  This flag is tested in ALTER TABLE only. It is
  ignored otherwise.