[1.1.X] Fixed #11949 -- Added a hook to allow ModelAdmin customization of the...

[1.1.X] Fixed #11949 -- Added a hook to allow ModelAdmin customization of the delete selected template. Thanks to bendavis78 for the report and patch, and Ramiro Morales for his cleanup work.

Backport of r12916 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12917 bcc190cf-cafb-0310-a4f2-bffc1f526a37