Update tracing functionality and add an ITX trace writer.

Update tracing functionality and add an ITX trace writer.

SConscript:
    Add build support for ITX trace writer
cpu/trace/reader/itx_reader.cc:
    Handle full 36 bit physical addressses.
cpu/trace/reader/itx_reader.hh:
    Need a string header file here
cpu/trace/trace_cpu.cc:
cpu/trace/trace_cpu.hh:
    Modify trace CPU to take a single trace and drive an instruction and data interfaces.

--HG--
extra : convert_revision : 4c81f2f9d9341df41f0ae45e4bda49800a43977c