configure: Add option to enable/disable libnfnetlink
Default behavior (autodetecting) does not change, but specifying
either option would explicitly disable or enable libnfnetlink support,
and if the library is not found in the latter case, ./configure will error
out.
Signed-off-by: Khem Raj <raj.khem@gmail.com> Signed-off-by: Maxin B. John <maxin.john@intel.com> Signed-off-by: Alexander Kanavin <alex@linutronix.de> Signed-off-by: Phil Sutter <phil@nwl.cc>