* Down-integrate internal changes to github.

* Fix BUILD file and regenerate csharp descritpor

* Down-integrate internal changes to github.

* fix csharp conformance test

* add comments in conformance.proto for text format

* fix comments

* fix comments, re-generated csharp file

* fix comments, re-generated csharp file

Even though the comments were indented to appear to go with the jspb
case/field, protoc doesn't collect comments like that, so these "hanging"
comments actually "attach" to the next thing added to each.  Looking at
https://github.com/protocolbuffers/protobuf/pull/5566 you see where
the generated code picked up the comment on the wrong field.

* 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

* Down-integrate internal changes

* Update generated code for php, objc and csharp.

* Add missing dependency in conformance_php

* Give a unique category to each test.

This change introduce a TestCategory enum to ConformanceRequest. Existing tests
are divided into three categories: binary format test, json format test and json
format (ignore unknown when parsing) test. For the previous two categories, there
is no change to existing testee programs. For tests with the last category, testee programs
should either enable ignoring unknown field during json parsing or skip the test.

* Fix python test

* Fix java

* Fix csharp

* Update document

* Update csharp generated code

* Enable ignoring unknown in json parsing in php

* Update generated descriptor files

* Update failure list for other languages.

* Remove unnecessary php files

* 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

Incase the different runtimes have different generation/implementations for
for the different primitive field types, cover a larger range of the proto
types in the oneof zero tests.

This was enabled by the recent open-sourcing of JSON
support and MessageDifferencer.

MessageDifferencer allows the conformance suite to expand
because it allows us to write tests for payloads that parse
successfully.  To verify the testee's output payload, we
need to parse it back into a message and compare the message
instances.  Comparing output bytes vs. a golden message is
*not* valid, because protobufs do not have a canonical
encoding (especially in the presence of maps, which have
no prescribed serialization order).

We only add one small JSON test for now, but with the
framework in place we now have the foundation to dramatically
expand the coverage of the conformance test suite.

Also added the ability for the testee to skip tests that
exercise features that are unimplemented.  This allows
Java (which currently has no JSON support) to skip tests
involving JSON.

Change-Id: I697b4363da432b61ae3b638b4287c4cda1af4deb

Change-Id: I382dcda97fa123a6da4ff5faad5d7ece95853f33

This allows us to enable conformance tests even when we know
that some tests are failing and need to be fixed.

Change-Id: I372f43663008747db6f2b2cf06e6ffa4c6d85b2d

Change-Id: I4c81808e6ace77d2b5737a43417045321b0b10f0

This is necessary for testing on iOS.

Change-Id: I54ec1e3aa2e9fbfff9a6cd6580920a6a62069b63

Change-Id: Ib75664194491643f8e4f1503a2ed942a2d1e1655

Change-Id: I34d301133eea9c6f3a822c47d1f91e136fd33145