Add more issues

[vstinner]

I create an issue with the content of todo.rst:

• https://hackerone.com/reports/26647 vulnerability.
• https://bugs.python.org/issue16611 BaseCookie now parses 'secure' and 'httponly' flags.
• https://bugs.python.org/issue22796 Regression in Python 3.2 cookie parsing
• https://bugs.python.org/issue25228 Support for httponly/secure cookies reintroduced lax parsing behavior
• https://code.djangoproject.com/ticket/26158 cookie parsing fails with python 3.x if request contains unnamed cookie

I just removed todo.rst.

[vstinner]

These are now old. I prefer to focus on new issues.