Simplify the pausing of CPU guard when blocked in debugger.
The pause/restore API in KJS::Interpreter is too subtle to use sanely in this context. Instead, merely ignore timeouts when blocked, and restart timers when unblocked.

This should eventually be replaced by a proper modality manager, so thinks like alert() work right, too, but I need to think it over some more. It is quite crucial, though, since there are quite some event looprecursion issues ATM.