Multiple input keys

[LPGhatguy]

We should be able to bind keys like shift+P. If a binding like this is set, then anything bound to just P should not trigger if shift is held down. This is how WoW works. Maybe there are cases where it shouldn't work this way?

[kpreid]

It might be desirable to allow overlap in some cases. For example, suppose shift (or even P) is bound to “show some additional information” or some other kind of innocuous modifier — then shift+P could still be a useful command if the other changes don't interfere.