mscoree: Implement DllGetClassObject

[Vincent Povirk]

You can't just use a static class factory for all the classes.

There's no need for GetIDispatchForObject when we already have
GetIUnknownForObject (and all you use is QueryInterface).

+    res = RegGetValueA( key, NULL, "Class", RRF_RT_REG_SZ, NULL,
classname, &dwBufLen);
We should probably use a W function here and convert to utf8, rather
than assume that's the default encoding.