Community modules patch: whitelist for mod_http_upload

[Nicolas Cedilnik]

Hello all,

This is my first patch submit. I hope I am using the right channel,
since this concerns prosody-modules and not core prosody.

This patches introduces a whitelist parameter for mod_http_upload,
something that can be useful for components, e.g.,
https://git.theta.eu.org/eta/whatsxmpp

If this is fine, I'll submit something similar for mod_http_upload_external.

XMPPingly yours,

-- Nicoco