github issue #828 - confuse monster effect when \

hero is invisible without being able to see invisible

Issue reported by EndHack:  you could see your hands glow red when
reading a scroll of confuse monster or casting the spell of confuse
monster even if you were unable to see yourself.

Switch to the blind feedback (tingling instead of glowing red) if
invisible without see invisible.

Also, have uncursed scroll or low skilled spell confer 1..2 turns
of glowing hands instead of always just 1.  (Blessed/highly skilled
stays at 2..9 turns.)

Fixes #828

src/uhitm.c

@@ -5435,17 +5435,21 @@ RESTORE_WARNING_FORMAT_NONLITERAL
 static void
 nohandglow(struct monst *mon)
 {
-    char *hands = makeplural(body_part(HAND));
+    char *hands;
+    boolean altfeedback;
 
     if (!u.umconf || mon->mconf)
         return;
+
+    hands = makeplural(body_part(HAND));
+    altfeedback = (Blind || Invisible); /* Invisible == Invis && !See_invis */
     if (u.umconf == 1) {
-        if (Blind)
+        if (altfeedback)
             Your("%s stop tingling.", hands);
         else
             Your("%s stop glowing %s.", hands, hcolor(NH_RED));
     } else {
-        if (Blind)
+        if (altfeedback)
             pline_The("tingling in your %s lessens.", hands);
         else
             Your("%s no longer glow so brightly %s.", hands, hcolor(NH_RED));