pgsql-server: Minor efficiency improvements in keeping track of trigger

Log Message:
-----------
Minor efficiency improvements in keeping track of trigger deferred
status.  In particular, I see no reason for deferredTriggerCheckState
to make an explicit entry to note that a particular trigger has its
default state --- that just clutters a list that should normally be
empty or very short.  I have plans to revise this module much more
heavily, but this is a simple separable improvement.

Modified Files:
--------------
    pgsql-server/src/backend/commands:
        trigger.c (r1.170 -> r1.171)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/trigger.c.diff?r1=1.170&r2=1.171)