VARIABLE_VALUE field is decreased to 1024 symbols.
(affected I_S tables: GLOBAL_VARIABLES, SESSION_VARIABLES,
 GLOBAL_STATUS, SESSION_STATUS).
The only variable which can be longer than 1024 is
init_connect. The variable will be truncated with warning.
Additional fix:
Added where condition filter which speed up queries which
have where condition with expressions which use VARIABLE_NAME
field.


mysql-test/r/information_schema.result:
  test result
mysql-test/r/show_check.result:
  result fix
mysql-test/suite/funcs_1/r/is_columns_is.result:
  result fix
mysql-test/t/information_schema.test:
  test case
sql/sql_show.cc:
  VARIABLE_VALUE field is decreased to 1024 symbols.
  (affected I_S tables: GLOBAL_VARIABLES, SESSION_VARIABLES,
   GLOBAL_STATUS, SESSION_STATUS).
  The only variable which can be longer than 1024 is
  init_connect. The variable will be truncated with warning.
  Additional fix:
  Added where condition filter which speed up queries which
  have where condition with expressions which use VARIABLE_NAME
  field.