Move op_class.hh out of encumbered/cpu/full and into cpu.

Move op_class.hh out of encumbered/cpu/full and into cpu.
Pull opClassStrings array out of encumbered/cpu/full/fu_pool.cc and move to
new cpu/op_class.cc file.

SConscript:
    Add new cpu-model-independent file to define OpClass enum strings.
cpu/op_class.hh:
    Fix comments etc.
cpu/static_inst.hh:
    op_class.hh moved to cpu directory

--HG--
rename : encumbered/cpu/full/op_class.hh => cpu/op_class.hh
extra : convert_revision : 314ac5ab7cc5c6a34b43dc1c2f2adc3e02f6d07f