Ruby: Conform to C89/C90 variable declaration rules.

Change-Id: I6cf77f01370204ad4bc7b345a040a9a3de1706a0

C# fix for TypeInitializer exception.

Add support for a file listing expected package to objc prefixes for validation.

- Add a env var to pass a set of expected prefixes for validation.
- Report warnings/errors based on the expected prefixes vs. the data in the files compiled.
- Use some helpers from common directory.

Fixed several Ruby conformance test cases through upb update.

Allow public access to descriptor.proto as a dependency.

With this in place, generating APIs on github.com/google/googleapis works - previously annotations.proto failed.
Currently there's no access to the annotations (stored as extensions) but we could potentially expose those at a later date.

Install protobuf from cmake project

Change-Id: Ief77de7134e05e07b1a7e3970d49880c2d5e6fe9

Link runtime statically for VS build

Revert "Add packFrom, unpackTo and is in google.protobuf.Any."

This reverts commit 7366efd8.

Still some discussion about the api to expose the helpers with.

Update GPBWellKnownTypes.m

More TODOs done.

- Removed a TODO without change in DescriptorPool.LookupSymbol - the TODOs were around performance, and this is only used during descriptor initialization
- Make the CodedInputStream limits read-only, adding a static factory method for the rare cases when this is useful
- Extracted IDeepCloneable into its own file.

Implement Keys and Values as views in MapField

 Make FieldDescriptor.IsPacked work appropriately.

Remove our own version of MakeTag now that the main one is fixed.

This is a bit of a grotty hack, as we need to sort of fake proto2 field presence, but with only a proto3 version of the descriptor messages (a bit like oneof detection).
Should be okay, but will need to be careful of this if we ever implement proto2.

Tidying up

Visual Studio is happy with it, but Mono isn't :(

Fix groups handling in C#

"Tested" by regenerating code and observing that there are no changes.

Down integrate. Generate a package name suffix ".nano" for nano messages

Remove unused .pb.h #includes.

Now the generated code doesn't need to check for end group tags, as it will skip whole groups at a time.
Currently it will ignore extraneous end group tags, which may or may not be a good thing.
Renamed ConsumeLastField to SkipLastField as it felt more natural.
Removed WireFormat.IsEndGroupTag as it's no longer useful.

This mostly fixes issue 688.

(Generated code changes coming in next commit.)