[RP] detect state of Mode_switch modifier?

[Joe Corneli]

I asked this question in the help-gnu-emacs list, but didn't hear
back, so I'm thinking that maybe this is "too low level" to be an
Emacs question and thought I'd try here, since this seems like
the sort of thing ya'll are knowledgeable about.

I want to have my Emacs cursor be one color when Mode_switch is
depressed and another when it isn't.  Since X knows when the modifier
is pressed/released, there is probably a way of passing this
information along to Emacs.  What would you suggest?

Joe