setup.py fixes for Python 3

Silence -Wsign-compare warning on Mac

Fixed Unused Parameter warning in headers.

Change references to `vector` to use `std::vector`

There is an example at the top of the page which contains code that appears to show a user how to create and serialize a message to a file. However the flags to open the file lack the O_CREAT flag which allows creating the file if it doesn't exist. I was troubleshooting a situation where this snippet was used and compiled, but never created a file.

Upstreaming patch used by Chromium in
https://codereview.chromium.org/693773003/

Includes files generated by each of:
   * autogen.sh
   * configure
   * make

Temporary change until a py3k-compatible google-apputils is released.

Release objects allocated by InitializeDefaultRepeatedFields()

Fix "warning C4018: '<' : signed/unsigned mismatch" 

Fix a bug that causes DynamicMessage.setField() to not work for repeated enum fields.

Fix descriptor validation logic for packed enum fields.

Explicitly specify pyext/cpp_message.py in py_modules list

enum fields.

Replace links to code.google.com/protobuf with developers.google.com/protocol-buffers

Add support for solaris atomicops