conversion scripts for gt-itm

[Haobo Yu <haoboy@isi.edu>]

I have a simple conversion program for gt-itm, it's at
http://www.isi.edu/~haoboy/files/sgb2ns.tar.gz. You may expand it into
gt-itm's directory then do make in sgb2ns/. Some pathnames and
library names in the Makefile need to be changed.

The program reads in gt-itm's standard topology file, and writes to
standard output a tcl function which generates the topology: 

proc create-topology ( ns node nmax linkBW )

Here node is the node array in the simulator, nmax is the number of nodes,
linkBW is the bandwidth of every link. It doesn't support different
bandwidth for different links but it's easy to add. The delay of links are
proportional to link length in the topology.

It is simple and ad hoc but worked for me.

- Haobo