Various serialization changes to make it possible for the O3CPU to checkpoint.

Various serialization changes to make it possible for the O3CPU to checkpoint.

src/arch/alpha/regfile.hh:
    Define serialize/unserialize functions on MiscRegFile itself.
src/cpu/o3/regfile.hh:
    Remove old commented code.
src/cpu/simple_thread.cc:
src/cpu/simple_thread.hh:
    Push common serialization code to ThreadState level.  Also allow the SimpleThread to be used for checkpointing by other models.
src/cpu/thread_state.cc:
src/cpu/thread_state.hh:
    Move common serialization code into ThreadState.

--HG--
extra : convert_revision : ef64ef515355437439af967eda2e610e8c1b658b