Move read/writeBlob functions to Port class;

Move read/writeBlob functions to Port class;
clean up implementation a little.

SConscript:
    Add mem/port.cc
cpu/simple/cpu.cc:
cpu/simple/cpu.hh:
    Move read/writeBlob functions to base Port class.
mem/port.hh:
    Implement read/writeBlob functions.
    No need for them to be virtual since the proxy
    object (now called TranslatingPort) is not a
    subclass of Port.
mem/port.cc:
    Implement read/writeBlob functions.

--HG--
extra : convert_revision : a3660eaa43a7c286aca962f17fa32fbd42bf1fa6