add system.mem_mode = ['timing', 'atomic']

add system.mem_mode = ['timing', 'atomic']
update scripts acordingly

configs/test/SysPaths.py:
    new syspaths from nate, this one allows you to set script, binary, and disk paths like
    system.dir = 'aouaou' in your script
configs/test/fs.py:
    update for system mem_mode
    Put small checkpoint example
    Make clock 1THz
configs/test/test.py:
src/arch/alpha/freebsd/system.cc:
src/arch/alpha/linux/system.cc:
src/arch/alpha/system.cc:
src/arch/alpha/tru64/system.cc:
src/arch/sparc/system.cc:
src/python/m5/objects/System.py:
src/sim/system.cc:
src/sim/system.hh:
    update for system mem_mode
src/dev/io_device.cc:
    Use time returned from sendAtomic to delay

--HG--
extra : convert_revision : 67eedb3c84ab2584613faf88a534e793926fc92f