This will cause failures if shared protos change in an incompatible
way.

* Fix php well known type conformance tests

* Properly generate code for test.proto

* Provide GPBMetadata files in c extensions for generated files to import.

* Remove unnecessary test

* Clean up code

* Add declaration for initOnce.

* Refactoring

* Add well known types to php runtime.

* Fix php7.0 tests

* No longer generate empty.proto in test as it has been included in
runtime.

* Fix zts build

* Clean code

* Rename g_p_b_empty to empty.

* Don't generate code for empty.proto in compatibility test

* Fix 32-bit

* Fix mac build

* Fix Makefile.am to add new files

It needs "-I" flag to find imported file google/protobuf/timestamp.proto

Jenkins complains for python 2.6
DEPRECATION: Python 2.6 is no longer supported by the Python core team
ERROR: InvocationError: '/tmp/protobuf/protobuf/python/.tox/py26-cpp/bin/python setup.py -q build_py'
https://grpc-testing.appspot.com/job/protobuf_pull_request/1502/testReport/junit/(root)/python_cpp/python_cpp/

This reverts commit 703f414c.

* Drop Python 3.3 from testing & add Python 3.5, 3.6

Python 3.3 goes [EOL](https://docs.python.org/devguide/index.html#branchstatus) next month.

* Sync test.sh with the Python versions in tox.ini

Exclude the unconfigured .pc input files of the CMake
based install: they shall not be packed/distributed,
only their outputs are

Exclude the unconfigured .pc input files of the CMake
based install: they shall not be packed/distributed,
only their outputs are

* Add php_generic_services option

* Generate PHP generic services

* Respect namespaces for generated PHP services

* Test PHP generated services

* Rename PHP generator service method doc comment function

* Correct phpdoc service method case

* Test namespaced PHP generic services

* Always use the FQCN for PHP generic service input/output

* Add generated_service_test to php test.sh

* Add php service test protos to CI

* Add php service files to php_EXTRA_DIST

* Use Interface suffix for php generic services

* Add json encode/decode for php.

* Fix php conformance test on 32-bit machines.

* Fix conformance test for c extension.

* Fix comments

* Add new file option php_namespace.

Use this option to change the namespace of php generated classes.
Default is empty. When this option is empty, the package name will be
used for determining the namespace.

* Uncomment commented tests

* Revert gdb test change

* Update csharp descriptor.

* Add test for empty php_namespace.

This has one important packaging change: the netstandard version now
depends (implicitly) on netstandard1.6.1 rather than on individual
packages. This is the preferred style of dependency, and shouldn't
affect any users - see http://stackoverflow.com/questions/42946951
for details.

The tests are still NUnit, but NUnit doesn't support "dotnet test"
yet; the test project is now an executable using NUnitLite. (When
NUnit supports dotnet test, we can adapt to it.)

Note that the project will now only work in Visual Studio 2017 (and
Visual Studio Code, and from the command line with the .NET Core
1.0.0 SDK); Visual Studio 2015 does *not* support this project file
format.

* Add compatibility test for php.

* Revert API incompatible change.

descriptor.proto uses proto2 syntax, which is not ready for external
usage. However, some proto3 files import descriptor.proto and cannot be
used. In this PR, all references (We cheated by only removing
extensions, which is enough for now. User should avoid using messages
defined in descriptor.proto as field type.) to content in
descriptor.proto are removed from generated files. Those that import
descriptor.proto can be used like other proto files.

This option will be prepended to generated classes of all messages in
the containing file.

This better shows the semantic of the API. For already setted fields,
mergeFromString do replacement for singular fields and appending for
repeated fields.

- Add entries to objectivec/DevTools/full_mac_build.sh
- Support `-quiet` via an option on full_mac_build.sh. NOTE: we don't use
  this on travis because the lack of output for a long time could cause travis
  to kill the build (when we get a slow VM).
- Update travis config to use newer images.

Missed in #2467.

1. Generate single file for each message.
2. Lazily initiate metadata.