Content-Disposition header should follow RFC-6266

When downloading a raw binary file with non-us-ascii name, Content-Disposition header reads like below:

Content-Disposition: inline; filename="日本語.pptx"

Here the filename is encoded in bare UTF-8. IE on Windows results this in corrupted filename like æ¥æ¬èª.pptx.

It should work fine with most of browsers incl. IE>9, FF, Chrome if it follows RFC-6266 like below:

Content-Disposition: inline; filename*=UTF-8''%E6%97%A5%E6%9C%AC%E8%AA%9E.pptx

GitLab CE ~~7.9.4~~ 7.11.4