Attempt to read load_base from memory when needed.

When creating the map list, always try and read the load base
using the memory functions for local unwinds. For remote unwinds,
if we can't map in the elf image, then try and use the memory
functions instead.

Bug: 21381155
(cherry picked from commit 849a547fb4de698b95c14806ddb3fcad8aa26331)

Change-Id: I96114e296ab1a0f7bfd51b3def1e2da90188249a
11 files changed