This is very WIP. 

The snmpd daemon's snmpd/main.c uses FreeBSD's 'struct cmsgcred' to verify
the identity of a peer process (see <sys/socket.h>). AFAICS, NetBSD
does not have an equivalent, so the build breaks here.

I'll leave it to more network code savvy people to find a workaround.

On top of that, the code has a few issues with signed vs. unsigned
char pointers (partly patched) that do not go down well with modern
gcc.
