* Don't modify share->base.born_transactional; now it is a value carved
in stone at creation time. share->now_transactional is what can be
modified: it starts at born_transactional, can become false during
ALTER TABLE (when we want no logging), and restored later.
* Not resetting create_rename_lsn to 0 during delete_all or repair.
* when we temporarily disable transactionality, we also change
the page type to PAGECACHE_PLAIN_PAGE: it bypasses some work in the
page cache (optimization), and avoids assertions related to LSNs.
* Disable INSERT DELAYED for transactional tables, because
durability could not be guaranteed (insertion may even not happen)


mysys/mf_keycache.c:
  comment
storage/maria/ha_maria.cc:
  * a transactional table cannot do INSERT DELAYED
  * ha_maria::save_transactional not needed anymore, as now instead
  we don't modify MARIA_SHARE::MARIA_BASE_INFO::born_transactional
  (born_transactional plays the role of save_transactional), and modify
  MARIA_SHARE::now_transactional.
  * REPAIR_TABLE log record is now logged by maria_repair()
  * comment why we rely on born_transactional to know if we should
  skipping a transaction.
  * putting together two if()s which test for F_UNLCK
storage/maria/ha_maria.h:
  ha_maria::save_transactional not needed anymore (moved to the C layer)
storage/maria/ma_blockrec.c:
  * For the block record's code (writing/updating/deleting records),
  all that counts is now_transactional, not born_transactional.
  * As we now set the page type to PAGECACHE_PLAIN_PAGE for tables
  which have now_transactional==FALSE, pagecache will not expect
  a meaningful LSN for them in pagecache_unlock_by_link(), so
  we can pass it LSN_IMPOSSIBLE.
storage/maria/ma_check.c:
  * writing LOGREC_REPAIR_TABLE moves from ha_maria::repair()
  to maria_repair(), sounds cleaner (less functions to export).
  * when opening a table during REPAIR, don't use the realpath-ed name,
  as this may fail if the table has symlinked files (maria_open()
  would try to find the data and index file in the directory
  of unique_file_name, it would fail if data and index files are in
  different dirs); use the unresolved name, open_file_name, which is
  the argument which was passed to the maria_open() which created 'info'.
storage/maria/ma_close.c:
  assert that when a statement is done with a table, it cleans up
storage/maria/ma_create.c:
  new name
storage/maria/ma_delete_all.c:
  * using now_transactional
  * no reason to reset create_rename_lsn during delete_all (a bug);
  also no reason to do it during repair: it was put there because
  a positive create_rename_lsn caused a call to check_and_set_lsn()
  which asserted in DBUG_ASSERT(block->type == PAGECACHE_LSN_PAGE);
  first solution was to use LSN_IMPOSSIBLE in _ma_unpin_all_pages() if
  not transactional; but then in the case of ALTER TABLE, with
  transactionality temporarily disabled, it asserted in
  DBUG_ASSERT(LSN_VALID(lsn)) in pagecache_fwrite() (PAGECACHE_LSN_PAGE
  page with zero LSN - bad). The additional solution is to use
  PAGECACHE_PLAIN_PAGE when we disable transactionality temporarily: this
  avoids checks on the LSN, and also bypasses (optimization) the "flush
  log up to LSN" call when the pagecache flushes our page (in other
  words, no WAL needed).
storage/maria/ma_delete_table.c:
  use now_transactional
storage/maria/ma_locking.c:
  assert that when a statement is done with a table, it cleans up.
storage/maria/ma_loghandler.c:
  * now_transactional should be used to test if we want a log record.
  * Assertions to make sure dummy_transaction_object is not spoilt
  by its many users.
storage/maria/ma_open.c:
  base.transactional -> base.born_transactional
storage/maria/ma_pagecache.c:
  missing name for page's type. Comment for future.
storage/maria/ma_rename.c:
  use now_transactional
storage/maria/maria_chk.c:
  use born_transactional
storage/maria/maria_def.h:
  MARIA_BASE_INFO::transactional renamed to born_transactional.
  MARIA_SHARE::now_transactional introduced.
  _ma_repair_write_log_record() is made local to ma_check.c.
  Macros to temporarily disable, and re-enable, transactionality for a
  table.
storage/maria/maria_read_log.c:
  assertions and using the new macros. Adding a forgotten resetting
  when we finally close all tables.