We use six sub-modules that aren't available in old versions. Not specifying
this requirement in the setup will lead to much less readable runtime errors.
It's particuarlly problematic for Mac OSX users because the system comes with
an old six version 1.4.1 by default.

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Change-Id: I6fa9f1b65d6c06b891aabf3f3d868364d74d727d

Change-Id: Ife609e073bd142d328b680c753f543bb18f4f66d

Change-Id: I1ee87c49481bcc545939745ccf0a53d766a01a4c

Change-Id: I4c4e2a4a248e4336fef735f75ff5648d8d33627e

Also delete some unused files.

Enabled JavaScript tests and added README.md.

The testee program crashes on some inputs.

Change-Id: Iab27b80e29b7a56c5bd7cb4724531ecf9bb2823a

Change-Id: Ia9e2795b1ff1abb30410ffb3ef96ba6f46dd99d0

The testee program of these two languages crashes on some test input.

Version number for beta languages is updated to v3.0.0-beta-2.
Version number for alpha languages is updated to v3.0.0-alpha-5.

The Java conformance test class uses JDK7+ only syntaxes and can't compile with JDK6.

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[skip ci]

Fix static non-pod type problem with dlopen

Add reference generator dependency

Drop all use of OSSpinLock

Apple engineers have pointed out that OSSpinLocks are vulnerable to live locking
on iOS in cases of priority inversion:
. http://mjtsai.com/blog/2015/12/16/osspinlock-is-unsafe/
. https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20151214/000372.html

- Use a dispatch_semaphore_t within the extension registry.
- Use a dispatch_semaphore_t for protecting autocreation within messages.
- Drop the custom/internal GPBString class since we don't have really good
  numbers to judge the locking replacements and it isn't required. We can
  always bring it back with real data in the future.

Add region tags to the Go protobuf examples.

Handle Any formatting for diagnostic purposes

Change-Id: Ibb3fe6f919cc7ca0df91da5e1697ba33d259e433

Make nuget package support coreCLR

Add JSON parsing to conformance tests.

This will allow us to like to specific snippets of code in the
documentation.  I plan to create a tutorial similar to the C# tutorial
https://developers.google.com/protocol-buffers/docs/csharptutorial

Since that tutorial has sections for populating a proto, parsing, and
serializing, I made a region for each of these for Go.  To make the
populating sample more self-contained, I refactor the listing example
slightly.

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.

Change-Id: I3daf32cb93dfe0fca38f8b48615ccfc307f748e9