max-cache-size doesn't work with 9.5.0b1

[Attila Nagy]

Hello,

I have a somewhat loaded caching only nameserver, running FreeBSD/amd64 7.0.

I decided to try 9.5.0 just to see how well it goes, but it turned out 
that its memory usage grows endlessly (OK, limited by the total VM space :).

I see this in top (the usage grows nearly every seconds, the machine 
gets some thousands queries per sec):
  PID USERNAME  THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
16969 bind        5  96    0   727M   723M select 0   8:51 68.12% named.950

The relevant parts from the config (cache-size set to very low, just to 
demonstrate the problem):
        max-cache-size 32M;
        cleaning-interval 15;

This is the case with and without ISC_USE_INTERNAL_MALLOC.

With 9.4.2 the memory usage does not grow above a given size:
17727 bind        5  97    0   131M   111M select 0  11:14 11.08% named.942