Completely re-work how the scons framework incorporates swig

and python code into m5 to allow swig an python code to
easily added by any SConscript instead of just the one in
src/python.  This provides SwigSource and PySource for
adding new files to m5 (similar to Source for C++).  Also
provides SimObject for including files that contain SimObject
information and build the m5.objects __init__.py file.

--HG--
extra : convert_revision : 38b50a0629846ef451ed02f96fe3633947df23eb

src/base/SConscript

@@ -97,3 +97,5 @@ Source('stats/visit.cc')
 if env['USE_MYSQL']:
     Source('mysql.cc')
     Source('stats/mysql.cc')
+
+PySource('m5', 'traceflags.py')