cpu: O3 add a header declaring the DerivO3CPU

SWIG needs a complete declaration of all wrapped objects. This patch
adds a header file with the DerivO3CPU class and includes it in the
SWIG interface.

--HG--
rename : src/cpu/o3/cpu_builder.cc => src/cpu/o3/deriv.cc

src/cpu/o3/SConscript

@@ -46,7 +46,7 @@ if 'O3CPU' in env['CPU_MODELS']:
     Source('bpred_unit.cc')
     Source('commit.cc')
     Source('cpu.cc')
-    Source('cpu_builder.cc')
+    Source('deriv.cc')
     Source('decode.cc')
     Source('dyn_inst.cc')
     Source('fetch.cc')