"mysql_upgrade (ver 5.1) add 3 fields to mysql.proc table but does
not set values".
            
mysql_upgrade (ver 5.1) adds 3 fields (character_set_client, 
collation_connection and db_collation) to the mysql.proc table, but 
does not set any values. When we run stored procedures, which were 
created with mysql 5.0, a warning is logged into the error log.
            
The solution to this is for mysql_upgrade to set default best guess
values for these fields. A warning is also written during upgrade, to
make the user aware that default values are set.

client/mysql_upgrade.c:
  Result lines which start with "WARNING" are passed through to the output. 
  This way we have a way of triggering WARNING-messages during upgrade 
  directly from the .sql-script.
mysql-test/r/mysql_upgrade.result:
  Expected result of the test.
mysql-test/t/mysql_upgrade.test:
  Added a test-case for the bug.
scripts/mysql_system_tables_fix.sql:
  The new fields are populated, and warnings are written.