to crash".
 Changes from snapshot innodb-5.0-ss52.
 Note that buf_block_t::index should be protected by btr_search_latch
 or an s-latch or x-latch on the index page.
 btr_search_drop_page_hash_index(): Read block->index while holding
 btr_search_latch and use the cached value in the loop. Remove some
 redundant assertions.
 Also fix 13778. When FOREIGN_KEY_CHECKS=0 we still need to check that
 datatypes between foreign key references are compatible.
 Also added test cases to 9802.