read: cfi parsing can't handle relocations for DW_EH_PE_pcrel

[philipc]

My strategy for handling relocatable addresses so far has been to override Reader::read_address/read_offset to store the relocation in a map and return an index into that map instead of the real address, and later convert it back when consuming the address. This doesn't work for parse_encoded_pointer because it doesn't use read_address/read_offset for relative pointers, and even if it did my strategy wouldn't work because parse_encoded_pointer needs to add the address to a base address.

I think the only fix for this is something like #409.

[philipc]

This strategy also doesn't work for range lists, because some values can be either an address or a special value (base addresses in <= v4 range list or tombstone in any version (#629)).