Remove redundant keys in CREATE TABLE and ALTER TABLE


mysql-test/r/constraints.result:
  Remove redundant keys
mysql-test/r/create.result:
  Remove redundant keys
mysql-test/r/innodb.result:
  Remove redundant keys
mysql-test/r/range.result:
  Remove redundant keys
mysql-test/t/range.test:
  Remove redundant keys
sql/sql_class.cc:
  Equality comparison of keys (ignoring name)
sql/sql_class.h:
  Equality comparison of keys (ignoring name)
sql/sql_table.cc:
  Remove redundant keys
sql/sql_yacc.yy:
  Introduce keys in child tables corresponding to FOREIGN KEYs