A couple of simply fixes/changes

Hi Kapil,

I finally got some time to look at the FReD again. Happy new year!

I merged from fred-dbg/fred and the forked from dmtcp/dmtcp. Now I can compile cleanly without any changes. I did a git diff against fred-dbg/fred and found only differences that I introduced.

The pull request I am sending contains a couple of simple things:

1) In README, the example gdb run is missing a "continue" between "break 30" and "fred-reverse-watch list_len(head)<17". Without it, it gets some FReD error and assertion failure.

2) In setup.sh, I made it such that if you pass DMTCP_ROOT on the command line it will use that instead of the "vanilla" path.

I was wondering if you have some bugs (minor, to begin with:) that you would like me to fix. I will be glad to get on it whenever I can.

Thanks!
Ning