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.

sql/sp.h

@@ -29,6 +29,7 @@
 #define SP_NO_DB_ERROR       -8
 #define SP_BAD_IDENTIFIER    -9
 #define SP_BODY_TOO_LONG    -10
+#define SP_FLD_STORE_FAILED -11
 
 /* Drop all routines in database 'db' */
 int