partial backport of bug43138 fix


mysql-test/r/warnings.result:
  test result
mysql-test/t/warnings.test:
  test case
sql/sql_class.cc:
  partial backport of bug43138 fix
sql/sql_class.h:
  partial backport of bug43138 fix
sql/sql_table.cc:
  partial backport of bug43138 fix