This added debug fission support.
It tries to find the dwp file from the debug dir /usr/lib/debug/*/debug
and read symbols from them.

Most of this patch comes from
https://critique.corp.google.com/#review/52048295
and some fixes after that.
The elf_reader.cc comes from TOT google code. I just
removed some google dependency.

Current problems from this patch
1: Some type mismatch: from uint8_t * to char *.
2: Some hack to find the .dwp file. (replace .debug with .dwp)

BUG=chromium:604440
R=dehao@google.com, ivanpe@chromium.org

Review URL: https://codereview.chromium.org/1884283002 .