Auto convert return addresses

This would change the behavior of ObjDumpAddressMap[address] where address would be a callstack return address instead of the offset address seen inside the dump file. This would require a change to ObjDumpAddressMap to be able to parse the page start and dump file offset for a binary from /proc/pid/maps. This should require no constructor change to ObjDumpAddressMap(path),

Start with ObjDumpAddressMap and its address lookup behavior, then inspect how /proc/pid/maps exposes the page start and dump-file offset for a binary. The work is done when ObjDumpAddressMap(path) accepts callstack return addresses without a constructor change and maps them to the corresponding dump offsets.

Written by the indexing model from the issue text.