[Users] ACC and DB support

[Bogdan-Andrei Iancu]

Hi there,

starting with the next release, the ACC module will be by default 
compiled with DB support - this does not involve any additional 
dependencies between external libs or internal module - the "db_url" 
parameter was moved to default value NULL which will prevent ACC module 
to use by default DB logging. To activate it, just set db_url to a valid 
URL.

So, ACC is compiled by default with DB support, but the DB support is by 
default disabled (via configuration).

I hope this will save a lot of trouble for users and for generating 
packages.

regards,
bogdan