Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/src/README.md

 Protocol Buffers - Google's data interchange format
 ===================================================
 
 [![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf) [![Build status](https://ci.appveyor.com/api/projects/status/73ctee6ua4w2ruin?svg=true)](https://ci.appveyor.com/project/protobuf/protobuf)
 
 Copyright 2008 Google Inc.
 
 https://developers.google.com/protocol-buffers/
 
 C++ Installation - Unix
 -----------------------
 
+To build protobuf from source, the following tools are needed:
+
+  * autoconf
+  * automake
+  * libtool
+  * curl (used to download gmock)
+  * make
+  * g++
+  * unzip
+
+On Ubuntu, you can install them with:
+
+  $ sudo apt-get install autoconf automake libtool curl make g++ unzip
+
+On other platforms, please use the corresponding package managing tool to
+install them before proceeding.
+
 If you get the source from github, you need to generate the configure script
 first:
 
     $ ./autogen.sh
 
 This will download gmock source (which is used for C++ Protocol Buffer
 unit-tests) to the current directory and run automake, autoconf, etc.
 to generate the configure script and various template makefiles.
 
 You can skip this step if you are using a release package (which already
 contains gmock and the configure script).
 
 To build and install the C++ Protocol Buffer runtime and the Protocol
 Buffer compiler (protoc) execute the following:
 
     $ ./configure
     $ make
     $ make check
-    $ make install
+    $ sudo make install
+    $ sudo ldconfig # refresh shared library cache.
 
 If "make check" fails, you can still install, but it is likely that
 some features of this library will not work correctly on your system.
 Proceed at your own risk.
 
-"make install" may require superuser privileges.
+For advanced usage information on configure and make, please refer to the
+autoconf documentation:
 
-For advanced usage information on configure and make, see INSTALL.txt.
+  http://www.gnu.org/software/autoconf/manual/autoconf.html#Running-configure-Scripts
 
 **Hint on install location**
 
   By default, the package will be installed to /usr/local.  However,
   on many platforms, /usr/local/lib is not part of LD_LIBRARY_PATH.
   You can add it, but it may be easier to just install to /usr
   instead.  To do this, invoke configure as follows:
 
     ./configure --prefix=/usr
 
@@ skipping 99 matching lines @@
 
   Compile using the IBM xlC C++ compiler as follows:
 
     ./configure CXX=xlC
 
   Also, you will need to use GNU `make` (`gmake`) instead of AIX `make`.
 
 C++ Installation - Windows
 --------------------------
 
-If you are using Microsoft Visual C++, see cmake/README.md.
+If you only need the protoc binary, you can download it from the release
+page:
 
-If you are using Cygwin or MinGW, follow the Unix installation
+  https://github.com/google/protobuf/releases
+
+In the downloads section, download the zip file protoc-$VERSION-win32.zip.
+It contains the protoc binary as well as public proto files of protobuf
+library.
+
+To build from source using Microsoft Visual C++, see [cmake/README.md](../cmake/README.md).
+
+To build from source using Cygwin or MinGW, follow the Unix installation
 instructions, above.
 
 Binary Compatibility Warning
 ----------------------------
 
 Due to the nature of C++, it is unlikely that any two versions of the
 Protocol Buffers C++ runtime libraries will have compatible ABIs.
 That is, if you linked an executable against an older version of
 libprotobuf, it is unlikely to work with a newer version without
 re-compiling.  This problem, when it occurs, will normally be detected
 immediately on startup of your app.  Still, you may want to consider
 using static linkage.  You can configure this package to install
 static libraries only using:
 
     ./configure --disable-shared
 
-Java and Python Installation
-----------------------------
-
-The Java and Python runtime libraries for Protocol Buffers are located
-in the java and python directories.  See the README file in each
-directory for more information on how to compile and install them.
-Note that both of them require you to first install the Protocol
-Buffer compiler (protoc), which is part of the C++ package.
-
 Usage
 -----
 
 The complete documentation for Protocol Buffers is available via the
 web at:
 
     https://developers.google.com/protocol-buffers/