banned file types

[Deeztek Support]

>
> For the hairy details of where the short extension comes from, see
> $map_full_type_to_short_type_re in the amavisd main file.
>

I'm trying to figure out where map_full_type_to_short_type_re is 
located. You said the amavisd main file, but I am running Ubuntu so I 
don't have an amavisd.conf file. Besides all that, I assume I can always 
add it to my 50_user file but where do I point it to? Where's the regex 
table that this line refers to? I can't seem to find ANY documentation 
as to exactly how map_full_type_to_short_type_re works exactly.

Thanks