- fixes (in recovery, checkpoint, log handler) of bugs found
during testing.
- new option --check for maria_read_log: with --only-display (which only
reads the header) it reads the full record, for debugging.


storage/maria/ma_loghandler.c:
  importing patch from Sanja for bug of translog_next_LSN() found
  during recovery
storage/maria/ma_loghandler_lsn.h:
  better types (0L is 4 bytes on some platforms, it causes problems
  when used into lsn_store(): right shift >= width of type.
storage/maria/ma_pagecache.c:
  work around infamous "PAGECACHE_PLAIN_PAGE used for transactional
  tables in specialm case"; REDO phase disables logging and this causes
  pages to be PAGECACHE_PLAIN_PAGE, thus ignored wrongly by the
  checkpoint taken at the end of the REDO phase.
storage/maria/ma_recovery.c:
  - a #ifdef which broke maria_read_log in non-debug builds (no output!)
  - support for maria_read_log --check
  - detect record corruption before opening the table
  - updating is_of_horizon requires writing the state
  - fix for wrong parsing of checkpoint record by recovery
storage/maria/ma_recovery.h:
  support for maria_read_log --check
storage/maria/maria_read_log.c:
  Option --check: --only-display only looks at the header;
  adding --check tries a translog_read_record() to see if record can
  be fully read (this is to find bugs).