fix #H4275 - blinded, stunned, confused timers

Blindness due to face covered by pie was ignored for several cases
of magically curing blindness--cleaning the face seems better than
adjusting timeout to account for u.ucreamed for those cases.  A few
instances of taking stun or confusion damage overrode existing stun
or confusion rather than increasing it.  Plus a copy/paste mistake
for dual stun+confusion when casting an expired spell.

There was also a suggestion that vomiting when already nauseated
should decrement the timer instead of increasing it.  But there is a
negative effect for as long as it's in effect, so I left that as is.

src/spell.c

@@ -866,8 +866,8 @@ int spell;
         break;
     case 7:
     case 8:
-        make_stunned(old_conf + 2L * duration / 3L, FALSE); /* 20% */
-        make_confused(old_stun + duration / 3L, FALSE);
+        make_stunned(old_stun + 2L * duration / 3L, FALSE); /* 20% */
+        make_confused(old_conf + duration / 3L, FALSE);
         break;
     case 9:
         make_stunned(old_stun + duration, FALSE); /* 10% */