Log Message:
Update protobuf to 2.6.1

Changelog:

2014-10-20 version 2.6.1:

  C++
  * Added atomicops support for Solaris.
  * Released memory allocated by InitializeDefaultRepeatedFields() and
    GetEmptyString(). Some memory sanitizers reported them as memory leaks.

  Java
  * Updated DynamicMessage.setField() to handle repeated enum values
    correctly.
  * Fixed a bug that caused NullPointerException to be thrown when
    converting manually constructed FileDescriptorProto to
    FileDescriptor.

  Python
  * Fixed WhichOneof() to work with de-serialized protobuf messages.
  * Fixed a missing file problem of Python C++ implementation.

2014-08-15 version 2.6.0:

  General
  * Added oneofs(unions) feature. Fields in the same oneof will share
    memory and at most one field can be set at the same time. Use the
    oneof keyword to define a oneof like:
      message SampleMessage {
        oneof test_oneof {
          string name = 4;
          YourMessage sub_message = 9;
        }
      }
  * Files, services, enums, messages, methods and enum values can be marked
    as deprecated now.
  * Added Support for list values, including lists of mesaages, when
    parsing text-formatted protos in C++ and Java.
      For example:  foo: [1, 2, 3]

  C++
  * Enhanced customization on TestFormat printing.
  * Added SwapFields() in reflection API to swap a subset of fields.
    Added SetAllocatedMessage() in reflection API.
  * Repeated primitive extensions are now packable. The
    [packed=true] option only affects serializers. Therefore, it is
    possible to switch a repeated extension field to packed format
    without breaking backwards-compatibility.
  * Various speed optimizations.

  Java
  * writeTo() method in ByteString can now write a substring to an
    output stream. Added endWith() method for ByteString.
  * ByteString and ByteBuffer are now supported in CodedInputStream
    and CodedOutputStream.
  * java_generate_equals_and_hash can now be used with the LITE_RUNTIME.

  Python
  * A new C++-backed extension module (aka "cpp api v2") that replaces the
    old ("cpp api v1") one.  Much faster than the pure Python code.  \ 
This one
    resolves many bugs and is recommended for general use over the
    pure Python when possible.
  * Descriptors now have enum_types_by_name and extension_types_by_name dict
    attributes.
  * Support for Python 3.