Currently the IDL find a parent type by a simple lookup of where
a symbol name maps directly to an AST node. This change provides
a mechanism for replacing the directy dictionary with a
version or version range based search.
BUG= http://code.google.com/p/chromium/issues/detail?id=87684
TEST= python idl_namespace.py
Review URL: http://codereview.chromium.org/7253025
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@91427 0039d316-1c4b-4281-b951-d872f2087c98