special columns are processed. This will be documented.
  Also some code cleanup and some changes to prepare the indexing of
  nullable columns (not achieve yet)

modified:
  storage/connect/colblk.cpp
  storage/connect/colblk.h
  storage/connect/connect.cc
  storage/connect/connect.h
  storage/connect/ha_connect.cc
  storage/connect/ha_connect.h
  storage/connect/macutil.cpp
  storage/connect/mycat.cc
  storage/connect/plgdbsem.h
  storage/connect/reldef.cpp
  storage/connect/reldef.h
  storage/connect/table.cpp
  storage/connect/tabmysql.cpp
  storage/connect/tabmysql.h
  storage/connect/tabodbc.h
  storage/connect/tabtbl.cpp
  storage/connect/tabutil.h
  storage/connect/value.h
  storage/connect/xindex.cpp
  storage/connect/xindex.h
  storage/connect/xtable.h