WL#5670: Remove SHOW NEW MASTER statement

NOTE: 2010-11-09: Feedback was solicited from stakeholders, but no decision has 
been made.
NOTE: 2010-11-24: ServerPT approved decision for removal in MySQL 5.5.

MySQL has an undocumented SHOW NEW MASTER statement that is unused. There is 
also a Com_show_new_master status variable that is mentioned only as a line in a 
summary table in the manual. The statement and the status variable should be 
removed.

The only mention of SHOW NEW MASTER occurs at
http://dev.mysql.com/doc/refman/4.1/en/news-4-0-4.html:

"
Disabled the use of SHOW NEW MASTER FOR SLAVE as this needs to be completely 
reworked in a future release.
"

It is evident that nothing was ever "reworked".

This WL task is a proposal is to remove SHOW NEW MASTER (and 
Com_show_new_master) immediately in MySQL 5.5.

We will forego the usual procedure of deprecating a feature in the current 
series and removing it later. The justification for this is that the feature is 
undocumented and unlikely to be in used by anyone.