Content filtering enabled

[Arran Cudbard-Bell]

Content filtering has now been enabled.

All HTML email will now automatically be converted to plaintext.

Only attachments with these content types will be accepted:

* multipart/mixed
* multipart/alternative
* text/plain
* image/svg+xml
* image/png

All others will be stripped.

Hopefully this will stop the majority of image banners, and work around
poorly behaved mail clients and users of those mail clients.

Arran Cudbard-Bell <a.cudbardb at freeradius.org>
FreeRADIUS development team

FD31 3077 42EC 7FCD 32FE 5EE2 56CF 27F9 30A8 CAA2