Recovery of state.records (the count of records which is stored into
the header of the index file). For that, state.is_of_lsn is introduced;
logic is explained in ma_recovery.c (look for "Recovery of the state").
The net gain is that in case of crash, we now recover state.records,
and it is idempotent (ma_test_recovery tests it).
state.checksum is not recovered yet, mail sent for discussion.
- WL#3071 Maria Checkpoint: preparation for it, by protecting
all modifications of the state in memory or on disk with intern_lock
(with the exception of the really-often-modified state.records,
which is now protected with the log's lock, see ma_recovery.c
(look for "Recovery of the state"). Also, if maria_close() sees that
Checkpoint is looking at this table it will not my_free() the share.
- don't compute row's checksum twice in case of UPDATE (correction
to a bugfix I made yesterday).


storage/maria/ha_maria.cc:
  protect state write with intern_lock (against Checkpoint)
storage/maria/ma_blockrec.c:
  * don't reset trn->rec_lsn in _ma_unpin_all_pages(), because it
  should wait until we have corrected the allocation in the bitmap
  (as the REDO can serve to correct the allocation during Recovery);
  introducing _ma_finalize_row() for that.
  * In a changeset yesterday I moved computation of the checksum
  into write_block_record(), to fix a bug in UPDATE. Now I notice
  that maria_update() already computes the checksum, it's just that
  it puts it into info->cur_row while _ma_update_block_record()
  uses info->new_row; so, removing the checksum computation from
  write_block_record(), putting it back into allocate_and_write_block_record()
  (which is called only by INSERT and UNDO_DELETE), and copying
  cur_row->checksum into new_row->checksum in _ma_update_block_record().
storage/maria/ma_check.c:
  new prototypes, they will take intern_lock when writing the state;
  also take intern_lock when changing share->kfile. In both cases
  this is to protect against Checkpoint reading/writing the state or reading
  kfile at the same time.
  Not updating create_rename_lsn directly at end of write_log_record_for_repair()
  as it wouldn't have intern_lock.
storage/maria/ma_close.c:
  Checkpoint builds a list of shares (under THR_LOCK_maria), then it
  handles each such share (under intern_lock) (doing flushing etc);
  if maria_close() freed this share between the two, Checkpoint
  would see a bad pointer. To avoid this, when building the list Checkpoint
  marks each share, so that maria_close() knows it should not free it
  and Checkpoint will free it itself.
  Extending the zone covered by intern_lock to protect against
  Checkpoint reading kfile, writing state.
storage/maria/ma_create.c:
  When we update create_rename_lsn, we also update is_of_lsn to
  the same value: it is logical, and allows us to test in maria_open()
  that the former is not bigger than the latter (the contrary is a sign
  of index header corruption, or severe logging bug which hinders
  Recovery, table needs a repair).
  _ma_update_create_rename_lsn_on_disk() also writes is_of_lsn;
  it now operates under intern_lock (protect against Checkpoint),
  a shortcut function is available for cases where acquiring
  intern_lock is not needed (table's creation or first open).
storage/maria/ma_delete.c:
  if table is transactional, "records" is already decremented
  when logging UNDO_ROW_DELETE.
storage/maria/ma_delete_all.c:
  comments
storage/maria/ma_extra.c:
  Protect modifications of the state, in memory and/or on disk,
  with intern_lock, against a concurrent Checkpoint.
  When state goes to disk, update it's is_of_lsn (by calling
  the new _ma_state_info_write()).
  In HA_EXTRA_FORCE_REOPEN, don't set share->changed to 0 (undoing
  a change I made a few days ago) and ASK_MONTY
storage/maria/ma_locking.c:
  no real code change here.
storage/maria/ma_loghandler.c:
  Log-write-hooks for updating "state.records" under log's mutex
  when writing/updating/deleting a row or deleting all rows.
storage/maria/ma_loghandler_lsn.h:
  merge (make LSN_ERROR and LSN_REPAIRED_BY_MARIA_CHK different)
storage/maria/ma_open.c:
  When opening a table verify that is_of_lsn >= create_rename_lsn; if
  false the header must be corrupted.
  _ma_state_info_write() is split in two: _ma_state_info_write_sub()
  which is the old _ma_state_info_write(), and _ma_state_info_write()
  which additionally takes intern_lock if requested (to protect
  against Checkpoint) and updates is_of_lsn.
  _ma_open_keyfile() should change kfile.file under intern_lock
  to protect Checkpoint from reading a wrong kfile.file.
storage/maria/ma_recovery.c:
  Recovery of state.records: when the REDO phase sees UNDO_ROW_INSERT
  which has a LSN > state.is_of_lsn it increments state.records.
  Same for UNDO_ROW_DELETE and UNDO_ROW_PURGE.
  When closing a table during Recovery, we know its state is at least
  as new as the current log record we are looking at, so increase
  is_of_lsn to the LSN of the current log record.
storage/maria/ma_rename.c:
  update for new behaviour of _ma_update_create_rename_lsn_on_disk().
storage/maria/ma_test1.c:
  update to new prototype
storage/maria/ma_test2.c:
  update to new prototype (actually prototype was changed days ago,
  but compiler does not complain about the extra argument??)
storage/maria/ma_test_recovery.expected:
  new result file of ma_test_recovery. Improvements: record
  count read from index's header is now always correct.
storage/maria/ma_test_recovery:
  "rm" fails if file does not exist. Redirect stderr of script.
storage/maria/ma_write.c:
  if table is transactional, "records" is already incremented when
  logging UNDO_ROW_INSERT. Comments.
storage/maria/maria_chk.c:
  update is_of_lsn too
storage/maria/maria_def.h:
  - MARIA_STATE_INFO::is_of_lsn which is used by Recovery. It is stored
  into the index file's header.
  - Checkpoint can now mark a table as "don't free this", and maria_close()
  can reply "ok then you will free it".
  - new functions
storage/maria/maria_pack.c:
  update for new name