See test maria-recovery.test for a model; all include scripts have
an "API" section at start if they do take parameters from outside.
* Fixing bug reported by Jani and Monty (when two REDOs about the same
page in one group, see ma_blockrec.c). 
* Fixing small bugs in recovery


mysql-test/include/wait_until_connected_again.inc:
  be sure to enter the loop (the previous query by the caller may not have
  failed: it could be
  query;
  mysqladmin shutdown;
  call this script).
mysql-test/lib/mtr_process.pl:
  * Through the "expect" file a test can tell mtr that a server crash
  is expected. What the file contains is irrelevant. Now if its last
  line starts with "wait", mtr will wait before restarting (it will
  wait for the last line to not start with "wait"). This is for
  tests which need to mangle files under the feet of a dead mysqld.
  * Remove "expect" file before restarting; otherwise there could be a
  race condition: tests sees server restarted, does something, writes
  an "expect" file, and then mtr removes that file, then
  test kills mysqld, and then mtr will never restart it.
storage/maria/ma_blockrec.c:
  - when applying a REDO in recovery, we don't anymore put UNDO's LSN on the page
  at once; indeed if in this REDO's group there comes another REDO
  for the same page it would be wrongly skipped. Instead, we keep
  pages pinned, don't change their LSN. When done with all REDOs
  of the group we unpin them and stamp them with UNDO's LSN.
  - fixing bug in applying of REDO_PURGE_BLOCKS in recovery: page_range
  sometimes has TAIL_BIT set, need to turn it down to know the real page
  range.
  - Both bugs are covered in maria-recovery.test
storage/maria/ma_checkpoint.c:
  Capability to, in debug builds only, do some special operations
  (flush all bitmap and data pages, flush state, flush log)
  and crash mysqld, to later test recovery.
   Driven by some --debug=d, symbols.
storage/maria/ma_open.c:
  debugging info
storage/maria/ma_pagecache.c:
  Now that we can _ma_unpin_all_pages() during the REDO phase
  to set page's LSN, the assertion needs to be relaxed.
storage/maria/ma_recovery.c:
  - open trace file in append mode (useful when a test triggers several
  recoveries, we see them all).
  - fixing wrong error detection, it's possible that during recovery
  we want to open an already open table.
  - when applying a REDO in recovery, we don't anymore put UNDO's LSN on the page
  at once; indeed if in this REDO's group there comes another REDO
  for the same page it would be wrongly skipped. Instead, we keep
  pages pinned, don't change their LSN. When done with all REDOs
  of the group we unpin them and stamp them with UNDO's LSN.
  - we verify that all log records of a group are about the same table,
  for debugging.
mysql-test/r/maria-recovery.result:
  result
mysql-test/t/maria-recovery-master.opt:
  crash is expected, core file would take room, stack trace would
  wake pushbuild up.
mysql-test/t/maria-recovery.test:
  Test of recovery from mysql-test (it is already tested as unit tests
  in ma_test_recovery) (WL#4137)
  - test that, if recovery is made to start on an empty table it can
  replay the effects of committed and uncommitted statements (having only
  the committed ones in the end result). This should be the first test
  for someone writing code of new REDOs.
  - test that, if mysqld is crashed and recovery runs we have only
  committed statements in the end result. Crashes are done in different
  ways: flush nothing (so, uncommitted statement is often missing
  from the log => no rollback to do); flush pagecache (implicitely flushes
  log (WAL)) and flush log, both causes rollbacks; flush log can also
  flush state (state.records etc) to test recovery of the state
  (not tested well now as we repair the index anyway).
  - test of bug found by Jani and Monty in recovery (two REDO about
  the same page in one group).
mysql-test/include/maria_empty_logs.inc:
  removes logs, to have a clean sheet for testing recovery.
mysql-test/include/maria_make_snapshot.inc:
  copies a table to another directory, or back, or compares both
  (comparison is not implemented as physical comparison is impossible
  if an UNDO phase happened).
mysql-test/include/maria_make_snapshot_for_comparison.inc:
  copies tables to another directory so that they can later
  serve as a comparison reference (they are the good tables,
  recovery should produce similar ones).
mysql-test/include/maria_make_snapshot_for_feeding_recovery.inc:
  When we want to force recovery to start on old tables, we prepare
  old tables with this script: we put them in a spare directory.
  They are later copied back over mysqltest tables while mysqld is dead.
  We also need to copy back the control file, otherwise mysqld,
  in recovery, would start from the latest checkpoint: latest
  checkpoint plus old tables is not a recovery-possible scenario of course.
mysql-test/include/maria_verify_recovery.inc:
  causes mysqld to crash, restores old tables if requested,
  lets recovery run, compares resulting tables with reference tables
  by using CHECKSUM TABLE.
  We don't do any sanity checks on page's LSN in resulting tables, yet.