* Fix more issues for reference values

* Revert change in gdb test

* Add more tests

* Fix empty FieldMask json encoding/decoding

* Add failed test to python's conformance failure list

* Fix c extension doesn' allow message reference in array

* Fix array constructor handling reference of array.

* Change test name

* Fixed compile warnings for PHP extension.

* Fixed some compile errors on PHP <7 and with TSR enabled.

* One more fix for TSRM builds.

* Fix field mask for php in json

* Update byte size

Added a few \ on the comments to match the exceptions scope when is referenced while in a namespace. So the IDEs can be happy.

* Fix Empty ListValue/Struct json encoding

* Add test for empty ListValue

* Fix Any json encoding/decoding in php

* Fix comments

* Inherit from message instead of implement

When regestering class (implmenets other class) during MINIT, zend_class_implements
would call zend_class_entry->interface_gets_implemented(). In PHP-7.3 interface_gets_implemented shares the same location with create_object.
However, during MINIT, the global object storeage hasn't been initialized. And thus, caused segment fault in php 7.3.

* Use zend_string_init where interned string may be the value.
zend_string_dup will keep using the existing interned string.
In php 7.3, interned string cannot be destroyed from user's code.

* Uncommment debug code

* Use latest phpunit for each php versions

* Revert change in Dockerfile

* Update php test to use the new docker image

* Update composer

* Change docker organization

* Update phpunit

* Debug phpunit

* Store phpunit into bin dir in docker image

* Install valgrind to docker

* Fix compatibility test

* Remove generated_service_test from compatibility c extension test

* Update 32bit php test to the new docker image

* Install bison

* Fix build.sh

* Fix DOCKERIMAGE_PREFIX

* Fix basename

* Add comment to build_and_run_docker2.sh

* Remove commented code

* Fix comments

* Down-integrate internal changes

* Update generated code for php, objc and csharp.

* Add missing dependency in conformance_php

Replace update_version shell script with a python script, which is much better at handling XML rewrite. Update the PHP version too. As part of rewrite, some XML file format will change a little, but the semantics is still the same so it should be okay.

* adds string-to-int and int-to-string methods to enums

* remove check for valueToName property in EnumTrait

* Remove unused imports

* Update to avoid using EnumTrait

* Remove EnumTrait

* Update enum types

* Move name and value methods into generated classes

* Remove functions from GPBUtil

* Test well known enums

* Implement enum value to/from name in c extension

* Only generate use statement when namespace is present

* Add support for primitive types in setters

* Update to address PR feedback

* Add tests and fixes for repeated fields

* Remove repeated field code, add getters

* Cleanup, test getters and oneofs

* Move boxing logic into separate class

* Add tests for wrapper type constructor args

* Update to add new setXXXValue methods

* Fix tests for invalid values

* Fix c extension for wrapper accessors

* Fix the bug that well known types didn't call Message_construct

* Address PR comments

* Refactoring init message with array logic

* Add include path to protoc

* Add missing TSRM_LS defintion

* Fix TSRM_LS

* Fix dist check

* Adopt upb change for timestamp and duration json to php

* Remove unused code

* Re-sync upb

* Fix php implementation timestamp json parsing

* Fix strptime use local timezone on mac.

* Remove succeeding tests

* Resync

* Add tests for values

* Fix php tests

* Fix encoder handlers change default value

Previously, oneofsubmsg_handler and submsg_handler change zval's default value directly.
The fix use REPLACE_ZVAL_VALUE which create a copy of parsed value and assign it to zval.

* Fix well known type class not inheriting Message

Previously, well known types only implement Message interface but not inhert it.
Fix the problem by calling zend_do_inheritance

* Add back commented tests

* 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

* php: Added nanosecond support for Timestamp

* php: Fixed compatibility test

This change only makes assertEquals pass for message in c extension. However, it actually does nothing.
This is the same behavior before 3.6.0 release.

* Enable ignoring unknown in json parsing in php

* Update generated descriptor files

* Update failure list for other languages.

* Remove unnecessary php files

the testMessageSetNullFail function was declared twice.
So I renamed one to testMessageSetNullFailMap

Added `-y` flag to `sudo apt-get` command.

* Use legacy name in php runtime

Old generated code cannot work with new runtime, because the new runtime
assumes new class name for nested message. For details see #4738.

* Remove unused method