Unbrace
Fix Dith not actually increasing player stealth

This was broken by 560c0028.

Yred worshippers in umbras and players wearing the ring of shadows were
also less stealthy due to this bug.
Make !porr give exactly 6000 nutrition

It was raised to 6040 to compensate for the loss of the 40
nutrition that all potions once gave, but, well, that's not
actually a thing that needs to be compensated for.
flash the screen when exploring with monsters are in view

this should make it easier to see where monsters blocking your
autoexplore/travel are.

not sure what this will do for tiles, but... can fix it later if it's a
problem.