Repetitive code in RI triggers

Hi all,

I was looking through the RI triggers code recently and noticed a few 
almost identical functions, e.g. ri_restrict_upd() and 
ri_restrict_del(). The following patch is an attempt to reduce some of 
repetitive code. Yet there is still room for improvement.

Thanks,
-- 
Ildar Musin
i.musin@postgrespro.ru