* Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()


sql/item.cc:
   * More comments
   * Backport of safety measures from 5.0: make numeorous replaces:
      s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/item.h:
  Assert added
sql/item_cmpfunc.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/item_func.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/item_strfunc.h:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/item_subselect.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/item_sum.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/set_var.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/sql_base.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/sql_handler.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/sql_help.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()
sql/sql_select.cc:
  Backport of safety measures from 5.0: make numeorous replaces:
    s/item->fix_fields()/if (!item->fixed) item->fix_fields()