swift234

[python] Use PEP-0008 compliant code headers

Running the Python style guide checker
[`pep8`](https://pypi.python.org/pypi/pep8) on the Python code headers
in this repository results in the following error being emitted:

    $ pep8 utils/build-script
    utils/build-script:1:1: E265 block comment should start with '# '
    utils/build-script:3:1: E266 too many leading '#' for block comment
    utils/build-script:5:1: E266 too many leading '#' for block comment
    utils/build-script:6:1: E266 too many leading '#' for block comment
    utils/build-script:8:1: E266 too many leading '#' for block comment
    utils/build-script:9:1: E266 too many leading '#' for block comment
    utils/build-script:11:1: E265 block comment should start with '# '
    utils/build-script:11:80: E501 line too long (80 > 79 characters)

The problem is that the code header used in most Python files in the
repository:

1. Do not place a space in between `#` and the rest of the comment.
2. Contains some lines that just barely exceed the recommend length
   limit.

In addition, not all code headers in the repository follow the same
template.

This commit moves all Python code headers to the following template:

    # subfolder/file_name.py - Very brief description -*- python -*--
    #
    # This source file is part of the Swift.org open source project
    #
    # Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
    # Licensed under Apache License v2.0 with Runtime Library Exception
    #
    # See http://swift.org/LICENSE.txt for license information
    # See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
    #
    # -----------------------------------------------------------------------------
    #
    # This file contains stuff that I am describing here in the header and will
    # be sure to keep up to date.
    #
    # ----------------------------------------------------------------------------