REPLICATED WHEN SETTING DEFINER

Problem:
========
Privileges created by automatic_sp_privileges are not
correctly replicated when the procedure is created by a
super user using DEFINER.

Analysis:
========
when automatic_sp_privileges variable is set, the server
automatically grants the EXECUTE and ALTER ROUTINE
privileges to the creator of a stored routine, if the user
cannot already execute and alter or drop the routine. In
existing code when a privileged user creates a procedure
with DEFINER as a non privileged user on master the current
user is considered as privileged user and mysql.procs_priv
table will not be updated. Where as when the same statement
is replicated to slave, on slave the non privileged DEFINER
is considered as current user and privileges are getting
allocated. Hence there is a difference with respect to the
privileges that are allocated on master and slave. On slave
the creator of the stored routine should be considered
first.

Fix:
===
Binlog the creator of the stored routine along with the
query. With this on the slave first check if the creator
user exists on slave or not if available grant privileges to
creator. For back ward compatibility we use definer when
invoker is not available. We allow anonymous users to be
replicated from master to slave. Existing code has a
restriction of user.length > 0 which is not true in the case
of anonymous users. That restriction is removed now.