Remove usage of readdir_r() in Chromium code

readdir_r() is deprecated, which causes build failures when using
glibc-2.24 or newer headers.  This CL replaces usage of readdir_r()
with readdir(), and suppresses the warning for third_party code.

BUG=457759,751812
TBR=brettw@chromium.org

Change-Id: Idfeff0d535926bc53634a7574f00605c50d532ab
Reviewed-on: https://chromium-review.googlesource.com/599120
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Julien Tinnes <jln@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492190}
4 files changed