Implements #3380

* Delete unused files.

* Remove js_embed binary.

* Remove js_embed binary.

This reverts commit 724f0be3.

This lets all values of `WELL_KNOWN_PROTOS` be treated the same with
regard to Bazel's protobuf blacklisting.

We follow the findProtobuf.cmake naming convention
to ease the use of protobuf as cmake subproject

Add implementations of open(2), mkdir(2), stat(2),
etc. that support long paths under Windows (paths
longer than MAX_PATH in <windows.h>, which is 260
characters).

The implementations are in a separate namespace
(google::protobuf::internal::win32), so they won't
collide with the standard implementations in
<io.h>, but after importing them with `using` they
can be drop-in replacements.

Fixes https://github.com/bazelbuild/bazel/issues/2634
Fixes https://github.com/google/protobuf/issues/2891

tested only on windows with visual studio 2015 as generator

Unfortunate typo. Just one extra ',' symbol, has led to the hidden implicit behavior.

Now everything will be fine.

Until now this file was just checked into the repo, but actually it
should be generated from any.js, struct.js, and timestamp.js. This
change updates the build system to make this happen. To make it work I
also had to remove some C++11 features from embed.cc.

This pull request includes two implementation: C extension and PHP
package. Both implementations support encode/decode of singular,
repeated and map fields.

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

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

This could be tidied up significantly, and at some point we will want to parse the markdown and generate more appropriate XML - but this is definitely better than nothing.

Generated code changes coming in next commit.

Change-Id: Ieb7a2c2fbf35bc2a8fa65b915a5ecb68c83863e4

More tests required. Generated code in next commit.