Add gogo benchmark

Add dashboard support  

The compiler and util subpackages are created by the build_py class in
setup.py. This has caused an issue in the protobuf package in
conda-forge (https://github.com/conda-forge/protobuf-feedstock/issues/40),
which is fixed by this commit.

The SampleEnumMethod method was previously only called via
reflection, so the Unity linker thought it could be removed. Ditto
the parameterless constructor in ReflectionHelper.

This PR should avoid that issue, reducing the work needed by
customers to use Google.Protobuf from Unity.

Fix problem: cmake build failed in c++11  by clang

[C#] Update test project to be used with dotnet test and Visual Studio Test Explorer

CMakeLists.txt adds c++11 flags for clang

* Fix setup.py for windows build.

* Bump version number to 3.5.2

* Cat the test-suite.log on errors for presubits

Improve error message when googletest is missing.

Add support for Power (ppc64le) arch

Cleaner protoc artifacts

Update instructions about getting protobuf source.

Move ObjC WKTs to minimal imports to avoid import cycle.

Since the generated header import GPBProtocolBuffers.h, there is no need
to generate imports for the WKTs as they will have already been imported.

To ensure all headers aren't dependent on other things being imported
before/after them, make a source that just imports each header and add
it to the unittesting target, that way we ensure it can be included on
its own with ordering issues.

Also do this testing with a few generated headers that aren't part of
the library to help ensure the different generated imports needed are
complete.

To avoid a cycle between headers, have the WKTs use minimal imports instead
of using the helper to get everything from the library.

Fixes https://github.com/google/protobuf/issues/4301
Fixes https://github.com/google/protobuf/issues/4403

ENTRYPOINT is used even when other commands are specified on the "docker
run" command line. This allows running one-off commands in the docker
image (especially combined with volume binding with the host) with the
correct environment variables.

This is just better Dockerfile hygene as it produces smaller resulting
images with fewer useless files.

It is a bad idea to check out code into the docker image, as it will be
out-of-date. It is better to have the image just be the environment, and
let any scripts that need source check them out themselves.

This fixes #4419 in that it allows the image to build again, albeit
users would need to use wget to grab the source of the version of
protobuf they wish.

Cleanup LICENSE file.

Add kokoro build status badges.

Moved the badges to the language table as they are per-language based.
Some badges are not yet available due to stuck kokoro jobs.

Delete unused directories.

jenkins has been replaced by kokoro and we never use more_tests.

Removed atomicops.h stub