* Down integrate to github

Merge 3.7.x to master

Replaced shortn URL with intended URL.

* Revert "Revert "Fix Ruby module name generation when the ruby_package option is used (#5735)""

This reverts commit bb211e85.

* add new files to Makefile.am

* add frozen checks

* Use rb_check_frozen

* Correct assertion on frozen error message

The second argument for the method assert_raise is the message
to show when the assertion fails. It does not check the error
object's message.
Add an additional assertion that does check the error's message.

* do frozen check first

* example with extra enum method

* update expected test output

* slight simplification

* add test for generated enum helpers

* move const helpers to c extension

* more explicit test

* more explicit test

* indent

* add foo test

* add check for _const suffix

Updating Iterators to be compatible with C++17 in MSVC

* Update version number to 3.7.0

* Add php/releash.sh to Makefile.am

* Make cpp_distcheck exit on fail

Revert "Fix Ruby module name generation when the ruby_package option is used"

This reverts commit 9638dcc3.

* fix module name generation and add tests

* fix existing tests

* support both package name styles

* add check for overflow

* de-nestify

* break long lines

* let repeated fields push arrays

* add varargs push

* better test

* Fix construction of messages using the C++ Python implementation when a map field is passed from one message to another.

* Add a test on message map field construction

* python 3 support

* review comments

* add test

* Collapse code into one

Added Optional GRPC library to third party docs

down integration from internal

Cherry-pick fixing for mac tests after kokoro updates 

* fix macos build by changing xcode version

* add comments

* fix benchmark build for mac

* fix for gem option and install npm

* add test for node and npm

* fix node

* fix for node

* another attempts to fix node

* another attempts

* clean up

* Fix #5513

* Added tests for invalid lengths when reading strings and bytes.
Added test for reading tags with invalid wire types in unknown field set.
Changed invalid length check in ReadString to match the one in ReadBytes

We need to cast to a constant charpointer here.

* fix macos build by changing xcode version

* add comments

* fix benchmark build for mac

* fix for gem option and install npm

* add test for node and npm

* fix node

* fix for node

* another attempts to fix node

* another attempts

* clean up

* Add a script to mirror php changes to protobuf-php

* Create tag