[turba] Login capitalization is not respected

[Myke Place]

> 
> > Can Turba be changed to always write to the DB in a unified manner,
> > independent of the case of the username that Horde presents?
> 
> No. That would be a serious security flaw.
> 
> -chuck

It seems then, that Turba a user could login sucessfully into Horde, check 
all their mail in IMP, head over to Turba and view all of their contacts, 
but then are left wondering why they can't edit or delete some contacts. 
Is there a way to remedy this, other than somehow instructing users to 
always login using consistanatly upper or lowercase?

Thanks, as always, for your help Chuck.

-mp