This change only adds basic proto2 support without advanced features
like extensions, custom options, maps, etc.

The protoc binary now generates ruby code for proto2 syntax.
However, for now, it is restricted to proto2 files without advanced features
like extensions, in which case it still errors out.

This change also modifies the DSL to add proto messages to the DescriptorPool.
There is a new DSL Builder#add_file to create a new FileDescriptor. With this,
the generated ruby DSL looks something like:

Google::Protobuf::DescriptorPool.generated_pool.build do
  add_file "test.proto" do
    add_message "foo" do
      optional :val, :int32, 1
    end
  end
end

* objectivec: Quash -Wself-assign

* objectivec: Set -Wno-vla when building

Objective-C protobuf uses VLAs for performance reasons. Ensure Clang
doesn’t complain about them.

OnShutdownDelete shadowing issue

protobuf_generate(): add relative path to output dir

Without this fix, protobuf_generate() sets the variable _generated_srcs to
${protobuf_generate_PROTOC_OUT_DIR}/${_rel_dir}/${_basename}${_ext}
but generates the files in
${protobuf_generate_PROTOC_OUT_DIR}/${_basename}${_ext}

https://github.com/google/protobuf/issues/4887

* Enable ignoring unknown in json parsing in php

* Update generated descriptor files

* Update failure list for other languages.

* Remove unnecessary php files

Fix cpp benchmark dependency on mac

Merge 3.6.x into master

Fix initialization with Visual Studio

protoc-artifacts: Update centos base from 6.6 to 6.9

This avoids the need to use "yum update && yum upgrade" in the container
to be able to contact GitHub, which requires TLS 1.2[1].

I have verified that binaries built with this container still run in the
previous container; no errors like "/lib64/libc.so.6: version
`GLIBC_2.14' not found", which occur if using too new of a glibc when
compiling. CentOS 6.6 has glibc version 2.12 release 1.209.el6. CentOS
6.9 has glibc version 2.12 release 1.149.el6. Both would upgrade to
release 1.212.el6 via "yum update && yum upgrade".

1. https://githubengineering.com/crypto-deprecation-notice/

Updated Docker setup to use GCC 4.8

It appears that Visual Studio does not work well with std::once_flag
because it has a bug causing it to initialize that during dynamic
initialization instead of constant initialization. This change works
around the problem by using function static initializers instead.

@gerben-s originally wrote this change for the Google-internal codebase
but I am just cherry-picking it here.

This fixes #4773.

Fix SFINAE in 'RepeatedPtrFieldBase::Add'

Now that we depend on C++11, we need at least GCC 4.8 instead of 4.7.
This change updates the Docker setup to continue using CentOS 6.6 but
with GCC 4.8.

I also added libm to the whitelist for dynamically linked libraries for
the ARM64 protoc binary.

Without this the error of un-moveable GenericTypeHandler will pop until
'TypeHandler::New(arena_, std::move(value))' is called.

* Update message_module.cc

Add missing piece from pull request #4698:  actually initialize the new API object.

* Update message_module.cc

Fix bazel build of examples.

Add global extension registry to the repo.

* Add continuous test for ruby 2.3, 2.4 and 2.5

* Change ruby 2.5 to 2.5.0

* No need to provide argument to rb_funcall when argc is 0

* Fix tests for ruby 2.5

* Use rescue instead of assert_raise to accept subclass of error

Handle srcs in generated files by cd'ing in and out

Ruby JSON encoding omits zero-length repeated fields by default.

Feat: add import-style=commonjs_strict option to the compiler

Google::Protobuf::Struct can access a missing key (#3846)

Missing symbol exports for Windows DLL

Remove write-strings warning from COPTs

Add wsrpc

This should fix https://github.com/google/protobuf/issues/4717

This fixes issue #2610.

This was originally fixed in a101fa52 , but got
reverted by d36c0c53

Fix to allow a compilation under mips big endian with gcc

Internal convert file was broken. Change the capsule to the correct name