Remove all of the Tru64 specific stuff from the base System object

Remove all of the Tru64 specific stuff from the base System object
into its own Tru64System object.  Also remove the System builder
stuff and create a Tru64System builder.  This makes it much
simpler to support more operating systems.

arch/alpha/ev5.cc:
    Each system provides its own mechanism for doing a breakpoint.
base/remote_gdb.hh:
    #include <map>
cpu/pc_event.cc:
cpu/pc_event.hh:
    Separate out System specific PCEvents
cpu/simple_cpu/simple_cpu.cc:
    each system provides its own init script
kern/tru64/dump_mbuf.cc:
kern/tru64/printf.cc:
    Stick this in a namespace

--HG--
extra : convert_revision : 9f74527ed2ff8010431d9aff34357aaecc1fb3f6