Lookup a given Class object in the cache. If it does not exist,
check whether this is due to a class change and purge the caches
eventually.
Parameters: c - The class to look up. A ClassMap object or null if it does not exist in the cache.
Creates a class map for specific class and registers it in the
cache. Also adds the qualified name to the name->class map
for later Classloader change detection.
Parameters: c - The class for which the class map gets generated. A ClassMap object.