This is the manual code part of the Google.Protobuf library, and tests.
Some tests will fail until codegen is changed and rerun.

--pre is not necessary

Using binary one's complement to negate an unsigned int

Ran update_file_lists.sh to update Bazel and CMake file lists

Use the portable version of Log2Floor for Clang with older Android NDK versions

This is necessary for avoiding a strange compiler error that we have
already run into with older versions of Clang on NaCl.

This should fix Bazel builds, since those were missing a new file
(implicit_weak_message.cc).

This removes a Visual Studio warning:

warning C4146: unary minus operator applied to unsigned type, result
still unsigned.

--pre was not necessary to install google-protobuf when I tried it today (2017-12-06).

Integrated internal changes from Google

Sync benchmark changes from internal

Add a check_version() for use in WORKSPACEs

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.

Merge 3.5.x branch into master

* Provide discardUnknownFields API in php implementation

* Provide discardUnknownFields API in php c extension.

[Java] Add a UTF-8 decoder that uses Unsafe to directly decode a byte buffer.

Adding Release_CompareAndSwap 64-bit variant

unwrap descriptor class before comparison of RepeatedField types

Added back in LIBPROTOC_EXPORT which was removed by mistake

Upgrading dotnet to 1.0.4

[PROTOBUF-3404] add --with-zlib=PATH to configure.ac script

Add _file_desc_by_toplevel_extension back