Update //third_party/protobuf to version 3.

third_party/protobuf/autogen.sh

+#!/bin/sh
+
+# Run this script to generate the configure script and other files that will
+# be included in the distribution.  These files are not checked in because they
+# are automatically generated.
+
+set -e
+
+if [ ! -z "$@" ]; then
+  for argument in "$@"; do
+    case $argument in
+          # make curl silent
+      "-s")
+        curlopts="-s"
+        ;;
+    esac
+  done
+fi
+
+
+# Check that we're being run from the right directory.
+if test ! -f src/google/protobuf/stubs/common.h; then
+  cat >&2 << __EOF__
+Could not find source code.  Make sure you are running this script from the
+root of the distribution tree.
+__EOF__
+  exit 1
+fi
+
+# Check that gmock is present.  Usually it is already there since the
+# directory is set up as an SVN external.
+if test ! -e gmock; then
+  echo "Google Mock not present.  Fetching gmock-1.7.0 from the web..."
+  curl $curlopts -O https://googlemock.googlecode.com/files/gmock-1.7.0.zip
+  unzip -q gmock-1.7.0.zip
+  rm gmock-1.7.0.zip
+  mv gmock-1.7.0 gmock
+fi
+
+set -ex
+
+# TODO(kenton):  Remove the ",no-obsolete" part and fix the resulting warnings.
+autoreconf -f -i -Wall,no-obsolete
+
+rm -rf autom4te.cache config.h.in~
+exit 0