* Add conformance test for php c back

php c extension has different result for conformance test for different
php version and architecture. Try to add conformance back for php 7.1 c extension first.

* Disable conformance test for c extension on 32-bit architecture
32-bit and 64-bit have different failing tests

* Fix typo

* Store the class object itself

* Add test for backwards compatibility

* Rename and add test

* Add comments

Added support for Visual Studio 2017 in gitignore

* Prevents installation of `phpunit/phpunit:^6` because the test cases in this project require `\PHPUnit_Framework_TestCase` which was removed in v6. Moves generated PHP classes for tests into autoload-dev so that they are not referenced in the dist autoload. Adds Composer scripts to run protoc with and without grpc.

* update composer test target to use the same commands as generate_php_test_proto in tests.sh

* Remove/replace travis references.

Added Netifi Proteus to Registered Extensions

* php: Added nanosecond support for Timestamp

* php: Fixed compatibility test

When running unit tests, read reference files in text mode

This should put an end to all of the reports of unit test failures on
Windows machines.

* Delete unused files.

Sync internal benchmark changes

* upgrade dotnet SDK to 2.1.3 on kokoro linux

add php benchmark

Run autogen.sh in release script.

Add protoc release script for Linux build.

Add cpp tests under release docker image.

1. Added C++ tests under the release docker image.
2. Fixed a compile issue with the docker image.
3. Cleaned up tests.sh and removed traivis stuff.

Update protoc build scripts.

1. Changed maven script to only do artifact uploading and removed build
script invocation from it. We didn't use maven to invoke the build
script before (we built protoc manually and editted pom.xml to only do
uploading for previous releases), and will not use it in the future (we
will use kokoro to build artifacts).
2. Cleaned up build-protoc.sh and README.md: removed the part about
using maven to build and listed supported platforms explicitly.

Fix php tests

fix linux kokoro build in docker

fix commonjs js provide GOOGLE_CHECK

Compilation of Python wrappers fails with Python 3.7 because
the Python folks changed their C API such that
PyUnicode_AsUTF8AndSize() now returns a const char* rather
than a char*. Add a patch to work around. Relates #4086.

Add scripts for automated building of C# nuget on Kokoro