Fixed bug in duplicate key handling for block records during repair
All read-row methods now return error number in case of error
Don't calculate checksum for null fields
Fixed bug when running maria_read_log with -o


BUILD/SETUP.sh:
  Added STACK_DIRECTION
BUILD/compile-pentium-debug-max:
  Moved STACK_DIRECTION to SETUP
include/myisam.h:
  Added extra parameter to write_key
storage/maria/ma_blockrec.c:
  Added applying of undo for updates
  Fixed indentation
  Removed some not needed casts
  Fixed wrong logging of CLR record
  Split ma_update_block_record to two functions to be able to reuse it from undo-applying
  Simplify filling of packed fields
  ma_record_block_record) now returns error number on failure
  Sligtly changed log record information for undo-update
storage/maria/ma_check.c:
  Fixed bug in duplicate key handling for block records during repair
storage/maria/ma_checksum.c:
  Don't calculate checksum for null fields
storage/maria/ma_dynrec.c:
  _ma_read_dynamic_reocrd() now returns error number on error
  Rest of the changes are code simplification and indentation fixes
storage/maria/ma_locking.c:
  Added comment
storage/maria/ma_loghandler.c:
  More debugging
  Removed printing of total_record_length as this was always same as record_length
storage/maria/ma_open.c:
  Allocate bitmap for changed fields
storage/maria/ma_packrec.c:
  read_record now returns error number on error
storage/maria/ma_recovery.c:
  Fixed wrong arguments to undo_row_update
storage/maria/ma_statrec.c:
  read_record now returns error number on error (not 1)
  Code simplification
storage/maria/ma_test1.c:
  Added exit possibility after update phase (to test undo of updates)
storage/maria/maria_def.h:
  Include bitmap header file
storage/maria/maria_read_log.c:
  Fixed bug when running with -o