Log Message:
Updated protobuf to 3.3.0.

2017-04-05 version 3.3.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Planned Future Changes
  * There are some changes that are not included in this release but are
    planned for the near future:
      - Preserve unknown fields in proto3: please read this doc:

          \ 
https://docs.google.com/document/d/1KMRX-G91Aa-Y2FkEaHeeviLRRNblgIahbsk4wA14gRk/view

        for the timeline and follow up this github issue:

          https://github.com/google/protobuf/issues/272

        for discussion.
      - Make C++ implementation C++11 only: we plan to require C++11 to build
        protobuf code starting from 3.4.0 or 3.5.0 release. Please join this
        github issue:

          https://github.com/google/protobuf/issues/2780

        to provide your feedback.

  C++
  * Fixed map fields serialization of DynamicMessage to correctly serialize
    both key and value regardless of their presence.
  * Parser now rejects field number 0 correctly.
  * New API Message::SpaceUsedLong() that’s equivalent to
    Message::SpaceUsed() but returns the value in size_t.
  * JSON support
    - New flag always_print_enums_as_ints in JsonPrintOptions.
    - New flag preserve_proto_field_names in JsonPrintOptions. It will instruct
      the JSON printer to use the original field name declared in the .proto
      file instead of converting them to lowerCamelCase when printing JSON.
    - JsonPrintOptions.always_print_primtive_fields now works for oneof message
      fields.
    - Fixed a bug that doesn’t allow different fields to set the same json_name
      value.
    - Fixed a performance bug that causes excessive memory copy when printing
      large messages.
  * Various performance optimizations.

  Java
  * Map field setters eagerly validate inputs and throw NullPointerExceptions
    as appropriate.
  * Added ByteBuffer overloads to the generated parsing methods and the Parser
    interface.
  * proto3 enum's getNumber() method now throws on UNRECOGNIZED values.
  * Output of JsonFormat is now locale independent.

  Python
  * Added FindServiceByName() in the pure-Python DescriptorPool. This works only
    for descriptors added with DescriptorPool.Add(). Generated descriptor_pool
    does not support this yet.
  * Added a descriptor_pool parameter for parsing Any in text_format.Parse().
  * descriptor_pool.FindFileContainingSymbol() now is able to find nested
    extensions.
  * Extending empty [] to repeated field now sets parent message presence.

  PHP
  * Added file option php_class_prefix. The prefix will be prepended to all
    generated classes defined in the file.
  * When encoding, negative int32 values are sign-extended to int64.
  * Repeated/Map field setter accepts a regular PHP array. Type checking is
    done on the array elements.
  * encode/decode are renamed to serializeToString/mergeFromString.
  * Added mergeFrom, clear method on Message.
  * Fixed a bug that oneof accessor didn’t return the field name that is
    actually set.
  * C extension now works with php7.
  * This is the first GA release of PHP. We guarantee that old generated code
    can always work with new runtime and new generated code.

  Objective-C
  * Fixed help for GPBTimestamp for dates before the epoch that contain
    fractional seconds.
  * Added GPBMessageDropUnknownFieldsRecursively() to remove unknowns from a
    message and any sub messages.
  * Addressed a threading race in extension registration/lookup.
  * Increased the max message parsing depth to 100 to match the other languages.
  * Removed some use of dispatch_once in favor of atomic compare/set since it
    needs to be heap based.
  * Fixes for new Xcode 8.3 warnings.

  C#
  * Fixed MapField.Values.CopyTo, which would throw an exception unnecessarily
    if provided exactly the right size of array to copy to.
  * Fixed enum JSON formatting when multiple names mapped to the same numeric
    value.
  * Added JSON formatting option to format enums as integers.
  * Modified RepeatedField<T> to implement IReadOnlyList<T>.
  * Introduced the start of custom option handling; it's not as pleasant as it
    might be, but the information is at least present. We expect to extend code
    generation to improve this in the future.
  * Introduced ByteString.FromStream and ByteString.FromStreamAsync to
    efficiently create a ByteString from a stream.
  * Added whole-message deprecation, which decorates the class with [Obsolete].

  Ruby
  * Fixed Message#to_h for messages with map fields.
  * Fixed memcpy() in binary gems to work for old glibc, without breaking the
    build for non-glibc libc’s like musl.

  Javascript
  * Added compatibility tests for version 3.0.0.
  * Added conformance tests.
  * Fixed serialization of extensions: we need to emit a value even if it is
    falsy (like the number 0).
  * Use closurebuilder.py in favor of calcdeps.py for compiling JavaScript.