[imp] allow guests in IMP

[Chuck Hagenbuch]

Quoting Mathieu CLABAUT <mathieu.clabaut@free.fr>:

>   In today HEAD CVS, it seems that teh registry option allow_guests is
>   not anymore permitted for IMP.
> 
>   Is it a feature or a bug ?
> 
>   We were used to this feature.... (I undestand it may cause some
>   problem in case IMP is in charge of Auth for Horde.... but ...)

IMP doesn't work with allow_guests on, and never has. It requires a user to be 
logged in for it to make sense.

-chuck

--
Charles Hagenbuch, <chuck@horde.org>
"A dream which helps you to live your reality with dignity
 and justice is a good dream." - Tariq Ramadan