Add deprecation status columns to I_S.SYSTEM_VARIABLES

This would allow for easy / automated "is this server's config setting some deprecated variables" checks by running for example:

SELECT VARIABLE_NAME, GLOBAL_VALUE, DEFAULT_VALUE

  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES

  WHERE GLOBAL_VALUE_ORIGIN IN('CONFIG', 'SQL')

  AND IS_DEPRECATED = 'YES';

The new thing here is IS_DEPRECATED='YES'.
Note: this query will list all deprecated variables. See the comments below for how to filter for only changed variables.