FileAPI accepts invalid characters in filename

The FileAPI accepts files with filenames that contain characters which are illegal in some operating systems. This can cause issues when those files are created in a OS where the filename is legal, then downloaded to one where they are illegal.

Example:
A student using MacOSX creates a file and saves it as

 assignment_*NEW*_#2.docx 

. Student submits this file on a assignment module attempt.

A teacher using Windows Vista opens assignment module and selects "Download all submissions". The submission

 assignment_*NEW*_#2.docx 

is not displayed because it contains illegal characters in its filename.

Suggestion:
Clean filenames to strip characters / ? < > \ : * | " when a file is saved.