Added the code processing on expressions for applying
  multiple equalities.
sql_select.cc:
  Post-merge fixes for Item_equal patch.
  Added the code processing on expressions for applying
  multiple equalities.
Many files:
  Post-merge fixes for Item_equal patch.
item_cmpfunc.cc:
  Post-merge fixes for Item_equal patch.
  Fixed a problem when an equality field=const cannot be applied to
  the predicate P(field,c) for constant propagation as a conversion
  of field is needed.
item.h, item.cc:
  Fixed a problem when an equality field=const cannot be applied to
  the predicate P(field,c) for constant propagation as a conversion
  of field is needed.