Java files are moved to un-do the hack in the prevous commit, which
moved the java files to the original position for integration.

Move the original README.md to src since it's talking about C++
exclusively and add a more general README.md to document how
to install protoc for all languages.

Fixes google/protobuf#693

msan flags this as being undefined behavior. I think it's triggering
because the compiler has to insert a branch to avoid changing the
pointer's value if it starts out NULL. I can't figure out if this is
actually undefined behavior or not, but it definitely seems to be a gray
area of the standard which is best avoided.

"valueField": null

is parsed appropriately, i.e. that it remembers that the field is set.

On deserialization, missing values for message types
are replaced with a "default" message.

Defer calls to mutable_unknown_fields() until it is actually required to
save memory for C++ lite runtime.

Change-Id: Ica9c1fd276cdb164942d1e7b6e098c83ee3ffdc5

Change-Id: Ife609e073bd142d328b680c753f543bb18f4f66d

Change-Id: I4c4e2a4a248e4336fef735f75ff5648d8d33627e

Also delete some unused files.

Change-Id: Ibb3fe6f919cc7ca0df91da5e1697ba33d259e433

This addresses issue #1008, by creating a JsonFormatter which is private and only different
to JsonFormatter.Default in terms of reference equality.

Other plausible designs:

- The same, but expose the diagnostic-only formatter
- Add something to settings to say "I don't have a type registry at all"
- Change the behaviour of JsonFormatter.Default (bad idea IMO, as we really *don't* want the result of this used as regular JSON to be parsed)

Note that just trying to find a separate fix to issue #933 and using that to override Any.ToString() differently wouldn't work for messages that *contain* an Any.

Generated code changes follow in the next commit.

[skip appveyor]

Change-Id: I700f70e734abb6264db29369ecf227a9e1f783e7

This is adapted from the branch of @xfxyjwf at:

https://github.com/xfxyjwf/protobuf/commit/494716a682ef854168e92231a3cdcc89d587d9b9

and should solve the protobuf compilation problem against nvcc.

Tested against nvcc 6.5 and 7.0.

Adds support for buliding protobuf with emscripten; we just needed the proper platform define used in the right place.

There are corner cases where MessageDescriptor.{ClrType,Parser} will return null, and these are now documented. However, normally they *should* be implemented, even for descriptors of for dynamic messages. Ditto FieldDescriptor.Accessor.
We'll still need a fair amount of work to implement dynamic messages, but this change means that the public API will be remain intact.

Additionally, this change starts making use of C# 6 features in the files that it touches. This is far from exhaustive, and later PRs will have more.

Generated code changes coming in the next commit.

This changes csharp_names.h, which will require a corresponding change in GRPC.

Generated code coming in next commit - in a subsequent PR I want to do a bit of renaming and redocumenting around this, in anticipation of DynamicMessage.

In the old flow, any 2 char prefix in the expected file was still generating a
warning about being a poor prefix. Now we check the expected file first, so
anything expected is let through.

Instead of having a Proto nested namespace to avoid conflicts between the descriptor-holding static class and message classes, just append "Reflection" to the name.
Generated code changes (and corresponding manual changes) in following commit.

This fixes issue #832.

Generated code changes in next commit.

  1. mathlimits.h must be included before the inclusion of cmath (which
     gtest/gtest.h seems to include).
  2. hash function for StringPiece doesn't work.

Change-Id: I358a25d941a25b10b39fe76780eda41557699811

VC++ up to VS 2015 RTM does not require explicit storage allocation for
static const integers declared in classes. VS 2015 Update 1 requires
these storage definitions in some cases. It's unclear exactly what
cases - simple tests work with and without the explicit storage
allocation.

Many previous versions of VC++ have theoretically *allowed* a
definition to supply storage, but tests on VC++ 2013 show that this
doesn't actually work correctly - it leads to duplicate definition
errors in Chromium. So, the change is scoped to VS 2015 only.

This change also updates the generated files to match the new generator.

TL;DR - this change is necessary in order for Chromium to build with
VS 2015 Update 1.

The included C# test will fail until the regenerated code is used, which is in the next commit.

Change the #include for any.h to use angle brackets instead of quotes, to be consistent with other protobuf library includes.