group sensitive per user return attributes with rlm_sql

[Hugh Messenger]

> so do it in perl with rlm_perl :-)

I did think about that.  Trouble is, that means doubling up on the all the
group related queries.  First in the perl pre-process step, then in the
normal rlm_sql group processing.

By doing this as a patch to rlm_sql itself, I can cache the results of the
pre_process, and splice those into the original rlm_sql_process_groups
function, instead of running all the queries again.

May seem far fetched, given that I can't remember how to strcat properly!
But a lot of my old C chops are still there, it's just this darn string
concat that's giving me problems!

I'll see if I can dig up my (very!) old Kernighan and Ritchie.

> Peter Nixon

   -- hugh