[1.2.X] Fixed #14047 -- Updated the CommonMiddleware docs to include sending...

[1.2.X] Fixed #14047 -- Updated the CommonMiddleware docs to include sending broken link email notifications. Thanks to Leon Matthews for the report and patch.

Backport of [14532] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14353 bcc190cf-cafb-0310-a4f2-bffc1f526a37