Apply diff.txt from SF patch http://www.python.org/sf/561478
Apply diff.txt from SF patch http://www.python.org/sf/561478

This uses cgi.parse_header() in Checker.checkforhtml(), so that
webchecker recognises the mime type text/html even if options
are specified.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator