> How about rejecting null for the current loadLib

Yep, let's add a separate function for `dlopen(RTLD_SELF, ...)` later. The implementation is tricky, because which Library is returned depends on the caller, so this function could not live in druntime or we'd need to fake the return address.
No idea whether we can implement this semantic on Windows.
Maybe we could also come up with a better name than "loadLib no arguments".