platform2: move --std=gnu++11 flag to common-mk/common.gypi

A number of platform2 projects enabled C++11 features individually
in their .GYP files. Removed this flag from each of the projects
and added it to common.gypi for everyone to share.

BUG=None
TEST=Compile various platform2 targets to make sure they still compile.

Change-Id: I4136573ec5dcc988df2826056c8dae8847725504
Reviewed-on: https://chromium-review.googlesource.com/211534
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/crash_reporter/crash_collector.cc b/crash_reporter/crash_collector.cc
index d612ec7..f1dbb58 100644
--- a/crash_reporter/crash_collector.cc
+++ b/crash_reporter/crash_collector.cc
@@ -514,7 +514,7 @@
   std::string meta_data = StringPrintf("%sexec_name=%s\n"
                                        "ver=%s\n"
                                        "payload=%s\n"
-                                       "payload_size=%"PRId64"\n"
+                                       "payload_size=%" PRId64 "\n"
                                        "done=1\n",
                                        extra_metadata_.c_str(),
                                        exec_name.c_str(),