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.