Updates to make traces work correctly in all circumstances. Add opt set associative...

Updates to make traces work correctly in all circumstances. Add opt set associative simulation.

cpu/trace/opt_cpu.cc:
cpu/trace/opt_cpu.hh:
    Add the ability to simulate less than fully-associative opt caches.
cpu/trace/reader/itx_reader.cc:
    Add writeback to the command list.

--HG--
extra : convert_revision : a9c9c4be3358f4083d7e85772620441a3ad809db