online filter fails to identify which multi-memref for offline traces

#2439 (closed) added an online filter, but for offline traces it fails to indicate which memref passed the filter for a multi-memref instr. Today raw2trace always takes the first one. Perhaps we can fit an index # or sthg in the PC entry? (If we end up needing another entry we may as well just record whether a read or write and the size there.)