[1.0.X] Fixed #10254: Changed the regex in get_valid_filename to allow unicode...

[1.0.X] Fixed #10254: Changed the regex in get_valid_filename to allow unicode alphanumerics (thanks gulliver). Also updated the file_uploads test for this case to check the name after saving the uploaded file. As it was the test ensured that files with unicode characters in their names could be uploaded, but it wasn't actually ensuring that the unicode characters were preserved through save.

Backport of [10388]


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10389 bcc190cf-cafb-0310-a4f2-bffc1f526a37