Enlarge client user mode buffer, reduce client flags buffer

Enlarge client user mode buffer, reduce client flags buffer

We have to enlage our user mode buffer, so we can handle even unknown
user modes in the future; and reduce the client flags buffer, because
I can't imagine why we ever would need ~100 flags!?

Now we support up to 15 user modes (was: 8) and up to 15 flags (was: 99).

So in the end, we even save 99-15+8-15=77 bytes for each client structure!