This will allow SourceLink as per #4179, and mean that we can use C#
7.0 language features in the library (but not in generated code).
This does not affect which platforms we're *targeting*, so end users
won't see any difference.

It would be nice to update to 2.1.4, but AppVeyor's "Visual Studio
2017" environment is only 2.0.3.

Travis changed their default image:
https://blog.travis-ci.com/2017-11-21-xcode8-3-default-image-announce

So there is no need to set a specific image any more, and the non
apple language tests should be able to use the default images.

Stop having travis build the test matrix and make it explicit so extra
settings are only on the test that need the, this helps make the travis
UI a little cleaner (linux hosted stuff doesn't list an Xcode version),
as well as avoid unneeded requirements limiting the travis pool something
can run on.

Small improvements to objectivec/DevTools/full_mac_build.sh to avoid some
repeated scripting and hopefully make things more reliable work with Xcode
9.x.

Don't mark the iOS tests as able to fail, hopefully with the new settings
they are stable and won't give false signals.

Simplify the case for xcode versions and fixup xcode 9.[0-1].

Looking at tarvis history for master, jruby doesn't look like it has passed
in a really long time.  The other two tests have been failing for a few weeks.
Since travis has limited osx hosts, seems better to just remove things we
aren't expecting to pass.

This has one important packaging change: the netstandard version now
depends (implicitly) on netstandard1.6.1 rather than on individual
packages. This is the preferred style of dependency, and shouldn't
affect any users - see http://stackoverflow.com/questions/42946951
for details.

The tests are still NUnit, but NUnit doesn't support "dotnet test"
yet; the test project is now an executable using NUnitLite. (When
NUnit supports dotnet test, we can adapt to it.)

Note that the project will now only work in Visual Studio 2017 (and
Visual Studio Code, and from the command line with the .NET Core
1.0.0 SDK); Visual Studio 2015 does *not* support this project file
format.

- Add entries to objectivec/DevTools/full_mac_build.sh
- Support `-quiet` via an option on full_mac_build.sh. NOTE: we don't use
  this on travis because the lack of output for a long time could cause travis
  to kill the build (when we get a slow VM).
- Update travis config to use newer images.

- Let Xcode 8 update settings on the projects/schemes.
- Migrate Swift tests to Swift 3 syntax.
- Update the build/test script:
  - Require Xcode 8 (because of the Swift 3 requirement for tests)
  - Update the devices to what Xcode 8 has (8.x simulator seem to fail even
    though they can be downloaded in Xcode 8)
- Update the travis images to ones with Xcode 8.

The test is testing the binary/source compatibility between 3.0.0-beta-4
and the current version (right now it's 3.0.0).

Change-Id: Ic410b535758b38cee7baa99a15a0433734df44e6

When it runs in parallel with other jenkins tests, multiple tests start
to fail probably because cpp_distcheck will update the C++ lib that
other tests (such as python_cpp) are depending on.

Change-Id: Ibca0243084bb6b81c811b62c75288e20cc2aabf5

These tests are already covered by jenkins and right now jenkins can
finish these tests much quicker then travis.

Change-Id: I5799761ccc338211d750940e3cf4c8e2569c8144

1. Added ruby22 and jruby tests to jenkins.
2. Added javascript tests to jenkins.
3. Added golang tests to jenkins.
4. Removed ruby19/ruby20 tests from travis. Support for ruby 2.0 has
   ended since 2016/02/24.
   https://www.ruby-lang.org/en/news/2016/02/24/support-plan-of-ruby-2-0-0-and-2-1/

Change-Id: Ie984b06772335352a4be7067ab2485f923875685

1. Set JAVA_HOME so mvn can pick up the correct java version.
2. Remove jdk6 tests. It has been broken for a while and remain undetected as
   mvn is actually using java 7 to build the code. Given that we have
   set -source and -target to 6 in the pom.xml and the built .jar
   should be usable by java 6, having a dedicated java 6 test doesn't
   seem necessary (assuming very few Java 6 users want to compile protobuf
   Java from source).

Change-Id: I4f14da772632df3e47801f180198242b306c3f0f

This also updates the version number to 3.0.0-beta4

Move to dotnet cli for building, and .NET Core (netstandard1.0) as target platform

This also updates the version number to 3.0.0-beta4

Also hotwires updating ruby as CocoaPods was crashing within a support library.

Fixes #1619 

- Move the ObjC tests into the list and exclude them on linux, this will change
  where in the order they start, since they are longer, it will have other
  things run in parallel instead of them ending up last and taking the longest.
- Switch to the Xcode 7.3 image.
- Drop the use of xctool and stream line things through the full_mac_build.sh
  script. This means we end up with only one build script instead of two.
- Tweaks to the mac build script:
  - Make iOS Xcode version support explicit
  - Support Debug/Release only building
  - Change the OS X min parallel count to 2 to better deal with VMs.
- Split the travis ios tests into the two Xcode Configurations as the logs are
  choking travis.

Travis updated their images to include an xctool that can randomly kill
tests, so mark them as flaky to avoid turning things red.

In light of https://github.com/google/protobuf/issues/1232, disable the xctool
update so we stay on 0.2.7 which seems to work better.

Remove the passing of -newSimulatorInstance since the older xctool doesn't
support it.

- Update simulator versions used.
- Mark the iOS tests as flaky while trying to dig out the root cause.

- Let Xcode update the projects, schemes, and info.plists.
- Add workaround for shallow analyzer issues in current Xcode versions (deep analyze gets things correct).
- Tweak the Swift based tests to avoid warnings from Xcode 7's XCTest using optionals for autoenclosure results.
- No longer tag the ObjC iOS travis test as flaky, xctool seems to manage the simulator pretty well.