ltmain.sh, and missing from subdirectories. Autoconf automatically looks
in the parent directory for these files. I had to copy the files
depcomp, ltmain.sh, and missing into the root of the source tree.
(These get mapped to interfaces beginning with "net": net0, net1, etc.) I
originally planned to make this a debugging message to be displayed at a
certain debuggin level whether the interface type is recognized or not. It
looked to be a pain to give libdnet visibility of Nmap debugging level, so
instead it just prints a message to stderr only when the interface type is
unrecognized.
