Update for accurate unreadable elf files.

The functionality moved from the Unwinder object to the MapInfo
object and means that the individual unreadable files can be
displayed now.

Included adding the unreadable elfs per thread in the protobuf.

Updated the unwinder test.

Test: All unit tests pass.
Change-Id: I7140bde16938736da005f926e10bbdb3dbc0f6f5