execScan.c: in the end of scan projInfo->pi_slot must be

execScan.c: in the end of scan projInfo->pi_slot must be
	return, not a slot returned from access method (they have
	different TupleDesc and MergeJoin node was broken).
nodeIndexscan.c: index_markpos()/index_restrpos() call index-specific
	mark/restr funcs and are in use now (instead of
	IndexScanMarkPosition()/ExecIndexRestrPos()).