This needs to check for libusb-1.0. Since this shouldn't be linked to
the auxiliary programs, add another Makefile variable to record it in:
CPULIBS.
Stub out calls to outb() if it is unavailable, so that it can at least
use libusb in that case.
This only uses autoconf, not automake or libtool or intltool or whatever.
This also allows easy building of different emulators in different build directories.
I have tested TOPS-20 with pcap|tap+bridge, ITS with pcap|tun|tap+bridge, both on NetBSD and Linux
and hopefully everything still works after the fine-tuning.
