Drop libnet-config in v2.0

[robert-scheck]

As of writing, libnet-config gets always populated with libdir, even it's a standard path, e.g. libdir=/usr/lib or libdir=/usr/lib64. While this doesn't seem to be an issue, it practically leads to downstream (RPM) package conflicts for multilib architectures, where x86_64 and i686 packages are installed, because /usr/bin/libnet-config is accidentially different in these packages (example: https://src.fedoraproject.org/rpms/libnet/pull-request/2).

Thus the kind request is to only populate libdir in libnet-config, if libdir is not one of the default paths (that's something, that ./configure should be aware of).

[troglobit]

Patches to fix this are of course welcome. However, the recommended way today is using pkg-config. This is also stated at the top of libnet-config:

#   Kept for compatibility with existing projects.  For new
#   projects, or those looking to upgrade, we recommend the
#   new pkg-config framework, libnet.pc.  See the README.md
#   for details on how to use it.

If there turns out to be no interest from the community to fix this, my recommendation is to drop libnet-config (in favor of pkg-config) in the next major release.