During creation of the table list of
processed tables hidden I_S table 'VARIABLES'
is erroneously added into the table list.
it leads to ER_UNKNOWN_TABLE error in
TABLE_LIST::add_table_to_list() function.
The fix is to skip addition of hidden I_S
tables into the table list.


mysql-test/r/information_schema.result:
  test case
mysql-test/t/information_schema.test:
  test case
sql/sql_show.cc:
  The fix is to skip addition of hidden I_S
  tables into the table list.