Non-English filenames cause the file to not display

I have a Japanese site, in which the user's have attempted to upload files with Japanese characters in the filename. The upload then fails, and the flash is not displayed. I added a validation check so that only filenames with spaces, periods, hyphens, underscores, letters and numbers are allowed. I also added a note to the description of the file upload form element explaining this.

I am attaching the patch for the changes I made, though you don't need to use it if you don't want. But I would appreciate it if you could fix this problem in future versions of the module.