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.

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

Add _file_desc_by_toplevel_extension back for compatibility issue with 3.4.1.

_file_desc_by_toplevel_extension is a temporary solution for FieldDescriptor.file.
FieldDescriptor.file was added in code gen. However, we need to keep it for some time for compatibility reason (with 3.4.1 only). May try to remove it after 2 years.

Remove unhelpful build warnings

Include .cc and .h files in Python source distribution