Fix filenames

[RealGreenDragon]

Seems that filenames are URL-encoded twice (often only some characters, such as parenthesis), so web browsers cannot recognize filenames. This happens when the method 'RedirectDownload()' receive an URL-encoded $FileName. To fix simply URL-decode also the $FileName value.

[Th3-822]

Redirect download expects the filename (non urlencoded) as it's arguments (iirc i had removed it after noticing the double decoding downloading a file with % on it), if it's urlencoded then it would be a plugin issue (checking if the filename wasn't urldecoded from the link, etc.) or host issue (on it's C-D headers), that can be fixed using force_name on the plugin, or using CheckBack and "fixing" the header manually