* Compiler changes (extensions)

* Generated changes (extensions)

* Library changes (extensions)

* Adjusted a summary to indicate ContainingType can be null for extensions

* Compiler changes (custom option review + access level review)

* Generated code changes (custom options + access review)

* Library changes (custom options + access review)

* Support C# 6 with library changes

* Access HasValue by property

* Set access level of all extension classes to internal (revert in next PR)

* Added null checks to custom options

* Rebase on master and regenerate Conformance

* Removed second dictionary from ExtensionSet

* Rebased compiler changes

* Rebased generated code changes

* Rebased library changes + review changes

* Add more safety checks to extension accessors

* Remove instances where extension sets were unnecessarily allocated

* Remove cleared items from sets
Empty sets are now made null
IExtensionMessage -> IExtendableMessage

* Remove dead code from IExtensionValue impls

* Clean both repeated and single value extensions

* Add GetOrRegister method for repeated fields and allow clearing repeated extensions

* Add type safe ClearExtension methods, remove non-generic IExtendableMessage interface.

* Simplify ExtensionSet.TryMergeFieldFrom

* Rebase on master to resolve conflicts

* Fix Makefile.am

* Add ObjectIntPair to Makefile.am

* Add conformance test for nested listvalue

* Fix upb for parsing repeated Value/ListValue

* Add failed repeated ListValue conformance test into php failure list

* Modify how end tags are encounted in merge code (compiler)

* Modify how end tags are encounted in merge code (generated)

* Modify how end tags are encounted in merge code (library)

* Regenerate generated code through generate_descriptor_proto.sh

* Modify how end tags are encounted in merge code (compiler)

* Modify how end tags are encounted in merge code (generated)

* Modify how end tags are encounted in merge code (library)

* Regenerate generated code through generate_descriptor_proto.sh

* Down-integrate internal changes to github.

* fix python conformance test

* fix csharp conformance test

* add back java map_lite_test.proto's optimize for option

* fix php conformance test

Add group support for proto2

* Compiler changes

* Generated code changes

* Library changes

* Compiler style changes

* Generated style changes

* Fix Windows build errors

* Implement changes from review

* Reintroduce proto2 check

* Compiler changes (required handling review)

* Generated code changes (required handling review)

* Library changes (required handling review

* Field presence rewrite (compiler changes)

* Field presence rewrite (generated code changes)

* Compiler comment

* IFieldAccessor.HasValue library implementation

* Remove Clear methods and default values from proto3 code (Compiler)

* Remove Clear methods and default values from proto3 code (Generated)

* Remove Clear methods and default values from proto3 code (Library)

* Fix distcheck error

* Rewrite default string values to use base64 and convert

* Library changes (IMessage2)

* Compiler changes (IMessage2)

* Generated changes (IMessage2)

* Rebased and regenerated

* Compiler changes (initialized extension)

* Generated changes (initialized extension)

* Library changes (initialized extension)

* Refactor MessageExtensions.IsRequired

* Move string default value creator and bytes default value creator back to seperate methods

* Dead code cleanup

* Fixed segmentation fault
Removed unused header method declarations

* Edited MessageFieldGenerator to clone to backing field instead of property

* Generated C# proto code

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

* Add auto-generated header to C# generated files

* regenerate C# protos

 Add unknown field support for csharp

With this in place, all tests should pass.

Fixes #3725.

* Factored Conformance test messages into shared test schema.

* Updated benchmarks to use new proto3 message locations.

* Fixed include path.

* Conformance: fixed include of Python test messages.

* Make maven in Rakefile use --batch-mode.

* Revert changes to benchmarks.

On second thought I think a separate schema for
CPU benchmarking makes sense.

* Try regenerating C# protos for new test protos.

* Removed benchmark messages from test proto.

* Added Jon Skeet's fixes for C#.

* Removed duplicate/old test messages C# file.

* C# fixes for test schema move.

* Fixed C# to use the correct TestAllTypes message.

* Fixes for Objective C test schema move.

* Added missing EXTRA_DIST file.

Add more JSON tests around underscores

This should fix the failures in the conformance tests - although
it highlights the problem that we need to do this when changing
the conformance.proto file...

JSON tests fail, as we're not using OriginalNameAttribute yet.

The conformance tests now use types which are part of src/google/protobuf, so we need to include src in the proto path.
The notes around "fix-ups" have been out of date for some time now.

Generated code changes for previous commit (basically InternalBuildGeneratedFileFrom => FromGeneratedCode)

Other changes are due to the well-known types changing without us regenerating.

Completely untested so far - easier to get started in VS and then transfer to Linux for tweaking...