o rename unmarshalCode -> readCode, as it doesn't relate to Python's marshal
o zipimport shouldn't cacheCompiledSource (it's just been silently failing),
and use java enums

Files:
modified: /trunk/jython/src/org/python/modules/zipimport/zipimporter.java (try)
modified: /trunk/jython/Lib/pkgutil.py (try)
modified: /trunk/jython/src/org/python/core/imp.java (try)