From a bug report, flashing yourself
with a camera while in gremlin form blinded as with any other form, but
didn't inflict any damage the way that flashing a monster gremlin does.
This fixes that, and also makes light from wand/scroll/spell that hits
you-as-gremlin or monster gremlins do 1d5 damage too. It happens even
if the target is already in a lit spot, but doesn't continue afterwards:
simply being in a lit spot doesn't cause any damage, nor does lamp light.