Reviewed by Shinichiro Hamaji.

        Adjusted check-webkit-style so that files with file type NONE
        are automatically skipped without warning.

        https://bugs.webkit.org/show_bug.cgi?id=38197

        This change simplifies configuring which files to skip.  It also
        addresses an issue whereby check-webkit-style was unintentionally
        checking .vcproj files for carriage returns.

        * Scripts/webkitpy/style/checker.py:
          - Moved the C++, Python, and text file extensions to new
            module-level configuration variables.
          - Removed .pyc from the _SKIPPED_FILES_WITHOUT_WARNING configuration
            variable.
          - Changed the numeric values of the FileType enum so that
            FileType.NONE evaluates to False.
          - For ProcessorDispatcher.should_skip_without_warning():
            - Changed the method to return True for FileType.NONE files.
            - Made ChangeLog files an exception to getting skipped.
          - Changed the StyleProcessor.process() method to raise an
            exception if given a file path that should not be processed.

        * Scripts/webkitpy/style/checker_unittest.py:
          - Updated the unit tests and added more test cases as necessary.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@58401 268f45cc-cd09-0410-ab3c-d52691b4dbfc