config: Add a --without-python option to build process

Add the ability to build libgem5 without embedded Python or the
ability to configure with Python.

This is a prelude to a patch to allow config.ini files to be loaded
into libgem5 using only C++ which would make embedding gem5 within
other simulation systems easier.

This adds a few registration interfaces to things which cross
between Python and C++.  Namely: stats dumping and SimObject resolving

src/sim/debug.cc

@@ -29,8 +29,6 @@
  *          Steve Reinhardt
  */
 
-#include <Python.h>
-
 #include <string>
 #include <vector>
 
@@ -108,22 +106,6 @@ eventqDump()
     }
 }
 
-void
-py_interact()
-{
-    PyObject *globals;
-    PyObject *locals;
-
-    globals = PyEval_GetGlobals();
-    Py_INCREF(globals);
-    locals = PyDict_New();
-    PyRun_String("import code", Py_file_input, globals, locals);
-    PyRun_String("code.interact(local=globals())", Py_file_input,
-                 globals, locals);
-    Py_DECREF(globals);
-    Py_DECREF(locals);
-}
-
 int remote_gdb_base_port = 7000;
 
 int