if foreign_key_checks=0. (Bug #9802)


innobase/dict/dict0dict.c:
  dict_foreign_add_to_cache(): Add flag check_types.
  If the flag is FALSE, ignore character set mismatch.
innobase/dict/dict0load.c:
  dict_load_foreign(), dict_load_foreigns(): Add flag check_types.
  If the flag is FALSE, differences in character sets will be ignored.
innobase/include/dict0dict.h:
  dict_foreign_add_to_cache(): Add flag check_types.
  If the flag is FALSE, differences in character sets will be ignored.
innobase/include/dict0load.h:
  dict_load_foreigns(): Add flag check_types.
  If the flag is FALSE, differences in character sets will be ignored.
innobase/row/row0mysql.c:
  row_table_add_foreign_constraints(), row_rename_table_for_mysql():
  Pass trx->check_foreigns to dict_load_foreigns()
sql/ha_innodb.cc:
  ha_innobase::rename_table(): Clear trx->check_foreign if necessary.