Log Message:
Update to 2.5.0:

2013-02-27 version 2.5.0:

  General
  * New notion "import public" that allows a proto file to forward the \ 
content
    it imports to its importers. For example,
      // foo.proto
      import public "bar.proto";
      import "baz.proto";

      // qux.proto
      import "foo.proto";
      // Stuff defined in bar.proto may be used in this file, but stuff from
      // baz.proto may NOT be used without importing it explicitly.
    This is useful for moving proto files. To move a proto file, just leave
    a single "import public" in the old proto file.
  * New enum option "allow_alias" that specifies whether different \ 
symbols can
    be assigned the same numeric value. Default value is "true". \ 
Setting it to
    false causes the compiler to reject enum definitions where multiple symbols
    have the same numeric value.

  C++
  * New generated method set_allocated_foo(Type* foo) for message and string
    fields. This method allows you to set the field to a pre-allocated object
    and the containing message takes the ownership of that object.
  * Added SetAllocatedExtension() and ReleaseExtension() to extensions API.
  * Custom options are now formatted correctly when descriptors are printed in
    text format.
  * Various speed optimizations.

  Java
  * Comments in proto files are now collected and put into generated code as
    comments for corresponding classes and data members.
  * Added Parser to parse directly into messages without a Builder. For
    example,
      Foo foo = Foo.getParser().ParseFrom(input);
    Using Parser is ~25% faster than using Builder to parse messages.
  * Added getters/setters to access the underlying ByteString of a string field
    directly.
  * ByteString now supports more operations: substring(), prepend(), and
    append(). The implementation of ByteString uses a binary tree structure
    to support these operations efficiently.
  * New method findInitializationErrors() that lists all missing required
    fields.
  * Various code size and speed optimizations.

  Python
  * Added support for dynamic message creation. DescriptorDatabase,
    DescriptorPool, and MessageFactory work like their C++ couterparts to
    simplify Descriptor construction from *DescriptorProtos, and MessageFactory
    provides a message instance from a Descriptor.
  * Added pickle support for protobuf messages.
  * Unknown fields are now preserved after parsing.
  * Fixed bug where custom options were not correctly populated. Custom
    options can be accessed now.
  * Added EnumTypeWrapper that provides better accessibility to enum types.
  * Added ParseMessage(descriptor, bytes) to generate a new Message instance
    from a descriptor and a byte string.