nmsg has external library dependencies on libpcap, libprotobuf-c, libustr,
libwdns, and zlib.

nmsg will build with libpcap versions older than 1.0, but using an up-to-date
libpcap on Linux platforms is highly recommended due to support for PACKET_MMAP
capture sockets and changes in timeout handling.

Convenience copies of libprotobuf-c, libustr, and libwdns are included in the
nmsg distribution and will be compiled and linked in if these libraries are
not found on the system.

