Fix for BUG#24923: Functions with ENUM issues.

The problem was that the RETURNS column in the mysql.proc was of
CHAR(64). That was not enough for storing long-named datatypes.

The fix is to change CHAR(64) to LONGBLOB, and to throw warnings
at the time a stored routine is created if some data is truncated
during writing into mysql.proc.


mysql-test/r/sp.result:
  Update test result.
mysql-test/t/sp.test:
  Add a test case for BUG#24923.
scripts/mysql_system_tables.sql:
  Change the data type of column 'returns' from char(64) to longblob.
scripts/mysql_system_tables_fix.sql:
  Change the data type of column 'returns' from char(64) to longblob.
sql/sp.cc:
  Produce warnings if any data was truncated during writing
  into mysql.proc.
sql/sp.h:
  Add new error code.
sql/share/errmsg.txt:
  Add new error message.
sql/sql_parse.cc:
  Hande

scripts/mysql_system_tables_fix.sql

@@ -344,6 +344,7 @@ ALTER TABLE proc MODIFY name char(64) DEFAULT '' NOT NULL,
                              'MODIFIES_SQL_DATA'
                             ) DEFAULT 'CONTAINS_SQL' NOT NULL,
                  MODIFY body longblob NOT NULL,
+                 MODIFY returns longblob NOT NULL,
                  MODIFY sql_mode
                         set('REAL_AS_FLOAT',
                             'PIPES_AS_CONCAT',