Add proper support for embedded elf files.

- Add a method to get the max size of an elf file by reading the
  section header offset + size. This will properly map an elf
  file embedded into an apk, instead of just mapping in what is done
  by the dynamic linker. It does assume that the section headers are
  at the end of the elf file.
- Add new tests for the above functionality.
- Update the unwind_symbols tool to take an address for finding a
  function instead of dumping the entire symbol table.

Bug: 23762183

Test: Unit tests pass, unwind through the camera process and verify
Test: the GoogleCamera.apk shows some function names.
Change-Id: I00c021680fe1d43b60d652bf91bbf6667d9617be