Pick up changes from NetBSD:

Pick up changes from NetBSD:

    several files:

	date: 2006/02/27 15:53:24;  author: drochner;  state: Exp;
	avoid shadowing globals, for WARNS=2

	date: 2006/02/27 15:55:30;  author: drochner;  state: Exp;
	minor constification, good for WARNS=3 now

	date: 2006/02/27 15:57:17;  author: drochner;  state: Exp;
	NetBSD adaption:

		...

	-const pcap_strerror() for consistency

    gencode.c:

	date: 2006/04/26 09:24:33;  author: tron;  state: Exp;
	Add missing "const" keywords to match declarations in "pcap.h".

	date: 2006/10/15 19:27:21;  author: christos;  state: Exp;
	add a volatile variable to prevent vfork/longjmp clobbering.

    optimize.c:

	date: 2006/05/17 17:48:36;  author: drochner;  state: Exp;
	Make the optimizer use unsigned numbers as the kernel does.
	While it is not agreed on that purely unsigned arithmetics is nice,
	different behaviour of optimized and unoptimized code is less desirable.

    pcap-bpf.c:

	date: 2006/02/27 15:51:38;  author: drochner;  state: Exp;
	pull in from NetBSD's libpcap: use cloning bpf device on NetBSD

Have the configure script check for paths.h, so that we can include it
only if we have it, and use the cloning BPF device only if we're on
NetBSD *and* _PATH_BPF is defined (hopefully this will keep us from
using it on versions of NetBSD that don't have a cloning BPF device; if,
in the future, other OSes with BPF get cloning BPF devices, we can make
this work for them as well).