an assertion failure in debug builds when a context switch occurred in
buf_LRU_search_and_free_block() before the call to
btr_search_drop_page_hash_index() managed to acquire the mutexes again.

ha_node_t: Add the field buf_block_t* block.

ha_search_and_update_if_found(): Rename to ha_search_and_update_if_found_func()
with added buf_block_t* parameter in debug builds.  Define the wrapper macro
ha_search_and_update_if_found() that always takes the buf_block_t* parameter.

ha_insert_for_fold(): Rename to ha_insert_for_fold_func()
with added buf_block_t* parameter in debug builds.  Define the wrapper macro
ha_insert_for_fold() that always takes the buf_block_t* parameter.