Clearing away JSHint warnings

I used [JSHint](http://jshint.com) to look for potential sources of bugs. Originally, `jshint .` output about 80 warnings, but I was able to trim it down to 8.

    $ jshint .
    lib\multipart_parser.js: line 127, col 33, Expected a 'break' statement before 'case'.
    lib\multipart_parser.js: line 155, col 18, Expected a 'break' statement before 'case'.
    lib\multipart_parser.js: line 189, col 31, Expected a 'break' statement before 'case'.
    lib\multipart_parser.js: line 213, col 25, Expected a 'break' statement before 'case'.

    test\legacy\simple\test-file.js: line 9, col 19, 'test' is already defined.

    test\legacy\simple\test-incoming-form.js: line 18, col 19, 'test' is already defined.

    test\legacy\simple\test-multipart-parser.js: line 8, col 19, 'test' is already defined.

    test\legacy\simple\test-querystring-parser.js: line 7, col 19, 'test' is already defined.

    8 errors

These remaining warnings require a bit more work. I don't feel that I understand the codebase well enough to resolve these on my own, so I left them alone for now.