WL#8786: INFORMATION_SCHEMA WITH SHOW_COMPATIBILITY_56

This task is a follow up of WL#6629.

Deprecate cleanly INFORMATION_SCHEMA tables affected
by SHOW_COMPATIBILITY_56 = OFF.

User Documentation
==================

* http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-9.html
* http://dev.mysql.com/doc/refman/5.7/en/server-system-
variables.html#sysvar_show_compatibility_56
* http://dev.mysql.com/doc/refman/5.7/en/performance-schema-variable-table-
migration.html

The current behavior of the INFORMATION_SCHEMA for tables affected by
SHOW_COMPATIBILITY_56 = OFF is not satisfactory,
and causes confusion in tools or plugins.
This affects migration *FROM* the INFORMATION_SCHEMA tables.

When SHOW_COMPATIBILITY_56 = ON, there are no changes.

Functional Requirement 1
When SHOW_COMPATIBILITY_56 = OFF,
change the behavior of the server so that:
- (Req 1.1) SELECT FROM INFORMATION_SCHEMA.GLOBAL_STATUS
- (Req 1.2) SELECT FROM INFORMATION_SCHEMA.SESSION_STATUS
- (Req 1.3) SELECT FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
- (Req 1.4) SELECT FROM INFORMATION_SCHEMA.SESSION_VARIABLES
return an error (instead of an empty result set per WL#6629)

Also,
the current behavior of the PERFORMANCE_SCHEMA for tables affected by
SHOW_COMPATIBILITY_56 = ON is not satisfactory,
and causes complicated migration path for monitoring tools.
This affects migration *TO* the PERFORMANCE_SCHEMA tables.

When SHOW_COMPATIBILITY_56 = OFF, there are no changes.

Functional Requirement 2
When SHOW_COMPATIBILITY_56 = ON,
change the behavior of the server so that:
- (Req 2.1) SELECT FROM PERFORMANCE_SCHEMA.GLOBAL_STATUS
- (Req 2.2) SELECT FROM PERFORMANCE_SCHEMA.SESSION_STATUS
return the same result as with SHOW_COMPATIBILITY_56 = OFF.