delete __STDC_{FORMAT,LIMIT}_MACROS

With newer glibc versions (2.18+), these macros no longer exist (and the
functionality they protected are always enabled).  Delete them.

BUG=chromium:401360
TEST=precq passes

Change-Id: I21b0607a874b9f9e39dff050054a2928a6c55023
Reviewed-on: https://chromium-review.googlesource.com/262903


Trybot-Ready: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>