changed sendresult -> bool,tick,void as appropriate

changed sendresult -> bool,tick,void as appropriate
first crack at io devices code
made CpuRequest that derives from Request

dev/io_device.cc:
dev/io_device.hh:
    first crack at the classes for Pio and Dma devices
dev/platform.hh:
    We are going to a system pointer to get info about the memory system
mem/bus.hh:
    changed sendresult -> bool,tick,void as appropriate
mem/port.hh:
    changed sendresult -> bool,tick,void as appropriate;
    removed the sendTiming(pkt,t) call since it is not really
    implementable in a generic fashion
mem/request.hh:
    pulled items from Request into CpuRequest

--HG--
extra : convert_revision : 6213cf2b66417fa023b80884d9e623e78f5aa891