libdwfl: Fix and test aux_sym address_sync with relocated ELF

The aux_sym address_sync already worked with a full prelink, which has
.gnu.prelink_undo, but it failed on plain relocations with prelink -r.

Now it uses the difference in ehdr.e_entry as a first offset guess, and
the tests confirm this seems to work fine.

Signed-off-by: Josh Stone <jistone@redhat.com>
7 files changed