[RP] interactive switch

[Rupert Levene]

I wanted to run the resize command interactively in a script and found
RP lacking. Here's a patch to fix that:

http://rupert.dyndns.org/rp/#interactive

This adds a command-line switch, --interactive, which tells ratpoison
to give you the same behaviour when you send a remote command as you
get when you type commands directly into the input bar.

Rupert