Add preserve UnknownFields
Compare floating point values bitwise
Add auto-generated header to C# generated files

 Add unknown field support for csharp

This is the manual code part of the Google.Protobuf library, and tests.
Some tests will fail until codegen is changed and rerun.

* Add discard unknown API in ruby.

* Add test for oneof message field.

* Add TestUnknown to represent unknown field data clearly.

* Only serialize the message with unknown fields itself in test.

* Move discard_unknown from Message to Google.Protobuf

Fix up warnings from Xcode 9.1

unittest_proto3 had been changed in a very backward-incompatible
way which was never going to work with C# as it imports proto2 messages.

This is now a copy of the old file, but with a package name change for
compatibility with the remaining files in src/google/protobuf.

The other moves are for files that are only used by C#.

* 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

* Fix ruby segment fault

1) rb_ary_new cannot be called during allocate function. During allocate
fucntion, the containing object hasn't been marked and rb_ary_new may
invoke gc to collect containing object.
2) The global map should be marked before allocating it. Otherwise it
may be garbage collected.

* Add test

* Remove commented code

* Fix grammer error

* Enforce all error report for php tests.

* Import vendor/autoload.php in tests/bootstrap_phpunit.php

* Add php support for Timestamp.

* Fix comments

internal descriptor.proto

* Add any support in php runtime.

* Remove unused file in config.m4

* Fix comments

* Fix error for tsrmls build

* Add newly added file to Makefile.am

* Add descriptors test

* Update descriptors tests

* Add public descriptors

* Add test_desriptors.proto to test script

* Update composer files

* Remove references to GPBType, update tests to be compatible with c

* Update for c extension compatibility

* Remove nested enums for descriptor, update tests

* Strip leading '.' from descriptor name

* Update tests with test for getClass, fix OneofDescriptor

* Add new files to Makefile.am

* 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 scripts to build python wheel for linux.
Followed PEP513.

* Fix dist check for new added files.

* Update README for usage example.

* adds PHPDoc @return and @param for getters and setters respectively

* addresses changes in PR review

* adds documentation tests

* Update php_generator:

- Prepend \ to names where required
- Remove <pre> tags
- Update protobuf field comments

* Updates class files with the protobuf changes

* Addresses review comments

* removes Protobuf Type line from PHP generated classes

* fixes phpdoc test

* adds array types to phpdoc

* Follows proper autoloading standards
 - Splits PHP classes in descriptor.php into separate files
 - Splits MapFieldIter and RepeatedFieldIter into separate files
 - Moves descriptor.php to Internal/functions.php
 - Moves all namespaced functions into Iternal/functions.php

* fixes Makefile.am for added php files

* [PHP] moves all functions to GPBUtil

* removes description.php from the makefile

* 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.

- Fix up -copyWithZone: to not leave the two registries sharing
  some of the storage by using -addExtensions:.
- Improve -addExtensions: to clone the sub dict when there is
  nothing to merge into.
- A ExtensionRegistry unittests.
- Update project schemes to not have extra things in perf scheme.

* 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.