WL#1249: SHOW VARIABLES to show both server-side and client-side values

Affects: Server-7.1   —   Status: Un-Assigned   —   Priority: Medium

Some "server" variables like max_join_size and max_allowed_packet are 
specified on both the server side and the client side. Currently, the default 
values are (v. 4.1.0): 
 
Value       max_allowed_packet   max_join_size 
Client             16777216            1000000 
Server              1048576         4294967295 
 
The problem that is addressed by this worklog entry: It's impossible to tell 
from the client side (a) what is the actual value being used on the current 
conncetion, and (b) how did the server/client negotiate this value. The only 
manner in which we can get these values while connected are through SHOW 
VARIABLES, and this only provides us with the server values. 
 
Suggestion 
---------- 
1) Keep the current variable names, but change the semantics to reflect the 
*actual* values in use over the current connection 
2) introduce two new variables per existing variables, e.g. 
max_allowed_packet_server and max_allowed_packet_client, which will contain 
the values as defined by the server and client respectively.