mysql-test/t/key.test:
  Added SHOW CREATE TABLE, which is the proper way to check for table definitions
mysql-test/r/key.result:
  Fixed result after removing wrong bug fix
sql/table.cc:
  Reverted wrong bug fix.
  The intention with the original code was to show that MySQL treats the first
  given unique key as a primary key. Clients can use the marked primary key as a
  real primary key to validate row changes in case of conflicting updates.  The
  ODBC driver (and other drivers) may also use this fact to optimize/check
  updates and handle conflicts.  The marked key also shows what some engines, like InnoDB or NDB,
  will use as it's internal primary key.
  For checking if someone has declared a true PRIMARY KEY, one should use 'SHOW CREATE TABLE'