[1.1.X] Fixed #12898: Reverted a change that assumed the file system encoding...

[1.1.X] Fixed #12898: Reverted a change that assumed the file system encoding was utf8, and changed a test to demonstrate how that assumption corrupted uploaded non-ASCII file names on systems that don't use utf8 as their file system encoding (Windows for one, specifically). Thanks for the report to vrehak. 

r12661 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12662 bcc190cf-cafb-0310-a4f2-bffc1f526a37