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/mhitu.c

@@ -2147,10 +2147,15 @@ register struct attack *mattk;
                 /* not blind at this point implies you're wearing
                    the Eyes of the Overworld; make them block this
                    particular stun attack too */
-                if (!Blind)
+                if (!Blind) {
                     Your1(vision_clears);
-                else
-                    make_stunned((long) d(1, 3), TRUE);
+                } else {
+                    long oldstun = (HStun & TIMEOUT), newstun = (long) rnd(3);
+
+                    /* we don't want to increment stun duration every time
+                       or sighted hero will become incapacitated */
+                    make_stunned(max(oldstun, newstun), TRUE);
+                }
             }
         }
         break;