What OS-specific and OS-version-specific features tcpdump uses
*directly* should be checked for specifically; if it *requires* features
not available with systems using a 1.x kernel, the configure should fail
because of *that*, and if it doesn't require any such features, we
should allow building on/for systems with a 1.x kernel.
If there are issues with *libpcap* on systems with a 1.x kernel, then
that should be handled in the libpcap configure script - and, even if
it's impossible to capture traffic on such a system, you can build a
version of libpcap that can read files but not capture, which would give
you a tcpdump that could, at least, read files from other machines.