<Someone> reported that dowaternymph and dowaterdemon did not print a message
when their G_GONE checks failed. Now they do. I wasn't feeling
imaginative, so the the dowaterdemon message is the same as for no snakes.
This patch, based on code sent to us by <Someone> well over a year ago, addresses
bugs recently resurfaced. Namely, that lava does not generally do anything
to monsters or objects that land in java. Newly renamed minliquid() handles
both water and lava, and new fire_damage() is used similar to water_damage().
