After revision of the fix for bug #7520.
table.cc:
  Revised the fix for bug #7520.
  Made it compliant with 5.0 code where the bug does not exist.


sql/table.cc:
  Revised the fix for bug #7520.
  Made it compliant with 5.0 code where the bug does not exist.
mysql-test/r/select.result:
  After revision of the fix for bug #7520.