message: ek.Loop: automatically label variables
diff: import enoki
  import sys
  +import inspect
  from collections.abc import Mapping, Sequence
  VAR_TYPE_NAME = [
  @@ -549,10 +550,17 @@ def loop_process_state(loop, funcs, state, write):
  for func in funcs:
  values = func()
  +
  if isinstance(values, Sequence):
  for value in values:
  if hasattr(value, 'loop_put'):
  value.loop_put(loop)
  +
  + # Automatically label loop variables
  + cv = inspect.getclosurevars(func)
  + enoki.set_label(**cv.globals)
  + enoki.set_label(**cv.nonlocals)
  +
  del values
  assert old_state is None or len(old_state) == 0
  