Add CHECK_FOR_INTERRUPTS while decoding changes.

While decoding changes in a loop, if we skip all the changes there is no
CFI making the loop uninterruptible.

Reported-by: Whale Song and Andrey Borodin
Bug: 17580
Author: Masahiko Sawada
Reviwed-by: Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/17580-849c1d5b6d7eb422@postgresql.org
Discussion: https://postgr.es/m/B319ECD6-9A28-4CDF-A8F4-3591E0BF2369@yandex-team.ru

src/backend/replication/logical/reorderbuffer.c

@@ -2078,6 +2078,8 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 			Relation	relation = NULL;
 			Oid			reloid;
 
+			CHECK_FOR_INTERRUPTS();
+
 			/*
 			 * We can't call start stream callback before processing first
 			 * change.