* Down integrate to github

* 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

A bug was causing generated JSPB code with CommonJS-style imports to
refer incorrectly to nested messages from other .proto files. The
generated code would have things like "test_pb.InnerMessage" instead of
"test_pb.OuterMessage.InnerMessage". This commit fixes the problem by
correctly taking into account any message nesting.

Had to strip out some JSPB-format test code,
but also added some .proto test messages that
had been improperly stripped out.

A bug was causing generated JSPB code with CommonJS-style imports to
refer incorrectly to nested messages from other .proto files. The
generated code would have things like "test_pb.InnerMessage" instead of
"test_pb.OuterMessage.InnerMessage". This commit fixes the problem by
correctly taking into account any message nesting.

Had to strip out some JSPB-format test code,
but also added some .proto test messages that
had been improperly stripped out.

A couple of small tweaks were needed to fix test failures that were
inadvertently introduced in the last down integration. I also had to add
the map.js file which was missing.

This includes all internal changes from around May 20 to now.