another update to ovdb_server.c

[Heath Kehoe]

>
>  Haven't really been following this thread, but I've programmed with
>mmap on Solaris before, so I thought I'd chime in...
>
>  I belive that Solaris implements anonymous memory mapping by mapping
>the "/dev/zero" device.  According to Stevens (in UNIX Network
>Programming Volume 2, pg 315), this should also work on BSD systems
>after version 3.1, so you might find that you can get away with just
>using that, rather than checking for MAP_ANON* support and having
>different behaviors on different systems.
>

Except that not everyone has a /dev/zero (namely, HP/UX). 
I will mmap /dev/zero on those systems that don't have MAP_ANON*.

-heath