do R_ProcessEvents in rniIdle if Windows

Windows' graphic device (windows()) and pager freezes when waiting console user input, because Windows console, graphics device, pager share the same thread for event processing.

rniIdle is to called frequently when waiting console user input. So I added event processing for Windows in rniIdle function.

It seems like interrupted handling don't work in rniIdle so I avoided interrupted case(UserBreak).