B01003 - blindfold vs dust vortex

This started out as a change to address the strange sequence of messages if
you remove a blindfold while engulfed in a dust vortex.  That is addressed
by a new function that can be called in such situations.  Calls to this
function were added in all the cases where the can_blnd() engulfing
conditions end as a result of player action.  There are some other cases
that end ucreamed or usleep, but they happen between turns and shouldn't
need extra handling.

While I was at it, I noticed that a unicorn horn or prayer would cure
blindness even while engulfed in a dust vortex.  This is useless, because
you immediately get blind again the next turn.  So, I added checks to avoid
doing this.  Finally, it didn't make sense for eating a carrot to cure your
blindness in these situations either, only for it to return immediately.

doc/fixes35.0

@@ -22,6 +22,10 @@ apply weapon skill to-hit bonus or penalty to bare-handed attacks
 only give monk's "cumbersome armor" message when the armor penalty causes
 	an attack to miss
 identified touchstone can rub on gold like the data.base entry says
+dust vortex-induced blindness should kick in immediately when blindfold
+	is removed or glop is wiped off
+prayer/unicorn-horn won't fix blindness while still engulfed in a dust
+	vortex since it will just return immediately
 
 
 Platform- and/or Interface-Specific Fixes