Add index OID macro argument to DECLARE_INDEX

This patch changes places like this

DECLARE_UNIQUE_INDEX_PKEY(pg_aggregate_fnoid_index, 2650, on 
pg_aggregate using btree(aggfnoid oid_ops));
#define AggregateFnoidIndexId  2650

to this

DECLARE_UNIQUE_INDEX_PKEY(pg_aggregate_fnoid_index, 2650, 
AggregateFnoidIndexId, on pg_aggregate using btree(aggfnoid oid_ops));

and makes genbki.pl generate the #define's.  This makes the handling of 
catalog index OIDs consistent with the handling of catalog tables. 
Compare with:

CATALOG(pg_aggregate,2600,AggregateRelationId)