Enable proxies (Self/Parent) for specifying ports.

Significant revamp of Port code.
Some cleanup of SimObject code too, particularly to
make the SimObject and MetaSimObject implementations of
__setattr__ more consistent.
Unproxy code split out of print_ini().

src/python/m5/multidict.py:
    Make get() return None by default, to match semantics
    of built-in dictionary objects.

--HG--
extra : convert_revision : db73b6cdd004a82a08b2402afd1e16544cb902a4

src/python/m5/__init__.py

@@ -44,6 +44,7 @@ def panic(string):
     print >>sys.stderr, 'panic:', string
     sys.exit(1)
 
+# force scalars to one-element lists for uniformity
 def makeList(objOrList):
     if isinstance(objOrList, list):
         return objOrList
@@ -75,6 +76,7 @@ env.update(os.environ)
 # once the config is built.
 def instantiate(root):
     params.ticks_per_sec = float(root.clock.frequency)
+    root.unproxy_all()
     # ugly temporary hack to get output to config.ini
     sys.stdout = file(os.path.join(options.outdir, 'config.ini'), 'w')
     root.print_ini()