Byproducts of aborted attempt to refine 'parent' proxy semantics.

Mostly cleanup of mpy_importer.mpy_parse().

python/m5/__init__.py:
    Move panic() up to top in case we want to use it
    in mpy_importer (though I ended up not doing that
    after all).
python/m5/config.py:
    Add a couple of comments and a check for expressions
    like parent.any.foo (which is illegal).

--HG--
extra : convert_revision : dfc99ac9b1a2d91a736ca0b773b6d3c528a4f3cc

python/m5/__init__.py

@@ -1,14 +1,14 @@
 import sys, os
 
-# the mpy import code is added to the global import meta_path as a
-# side effect of this import
-from mpy_importer import AddToPath, LoadMpyFile
-
 # define this here so we can use it right away if necessary
 def panic(string):
     print >>sys.stderr, 'panic:', string
     sys.exit(1)
 
+# the mpy import code is added to the global import meta_path as a
+# side effect of this import
+from mpy_importer import AddToPath, LoadMpyFile
+
 # find the m5 compile options: must be specified as a dict in
 # __main__.m5_build_env.
 import __main__