additional key bindings for xterm

[Dan Nicolaescu]

xterm-216 when run like this:

xterm -xrm '*modifyOtherKeys:1'

emits distinct strings for key combinations that did not do anything
in the past, for example C-. C-, C-TAB C-return 
This allows emacs to use these keys when running in such an xterm. 
For example the C-. binding in flyspell-mode was only usable in X, but
not in a terminal in the past. 

What other keys would be useful for emacs to support? Please give
specific examples so they can be added to term/xterm.el

Thanks

        --dan