[1.1.X] Fixed #12445 -- Added ' (single quote), @ (at sign), and ~ (tilde) to...

[1.1.X] Fixed #12445 -- Added ' (single quote), @ (at sign), and ~ (tilde) to safe characters in `iri_to_uri` function.

Backport of r12066 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12067 bcc190cf-cafb-0310-a4f2-bffc1f526a37