Require VS2015 in the solution file

Add atomics support for 32-bit PPC.

Added support for CommonJS require()

Support ObjC Generic Collections

Validate that end-group tags match their corresponding start-group tags

Some fixes for the most recent release notes.

- Extend GPB*ObjectDictionary to support generic syntax.
- Update the generator to output generics so the enclosed type is exposed for compiler checks.
- Use generics in a the public interfaces.
- Update the generated sources that are checked in.

"nodejs" does not exist on Travis, it appears.

List python_cpp as failing on OS X

Disable the xctool updates

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.

Generate C# code whenever descriptor.proto changes

Added ALLOW_UNLIMITED_BINARY_PROTO macro and setting it when

Add more tests around merging wrappers

Removes redundant null pointer checks checks

Removed 'optional' from proto3 syntax file.

--allow_oversize_protos=true is passed to bazel build.
When this macro is set, SetTotalBytesLimit is called to remove
the 64MB limit on binary protos when during ParseFromString.

Move the xctool use of -reporter into a common spot and always use "plain" to get more readable logs on travis.

Move the xctool use of -reporter into a common spot and always use "plain" to get more readable logs on travis.

Tweak the xctool run for iOS tests to try and sort out flake

- Use the plain reporter for slightly more readable logs.
- Add -newSimulatorInstance to the run-tests to see if it helps with flake.

Bump up travis to Xcode 7.2

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