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>
diff --git a/update_engine.gyp b/update_engine.gyp
index 86981d0..8ac39ec 100644
--- a/update_engine.gyp
+++ b/update_engine.gyp
@@ -27,7 +27,6 @@
       '-Wl,--gc-sections',
     ],
     'defines': [
-      '__STDC_FORMAT_MACROS=1',
       '_POSIX_C_SOURCE=199309L',
       'USE_HWID_OVERRIDE=<(USE_hwid_override)',
       'USE_MTD=<(USE_mtd)',