new property: BLND_RES

Add enlightenment feedback for Sunsword's blocking of becoming blind
from light flashes.  It uses an extra property so that wizard mode
can report the reason.

EDITLEVEL is being incremented, so existing save and bones files are
invalidated.

src/insight.c

@@ -1533,6 +1533,9 @@ attributes_enlightenment(
     /*** Vision and senses ***/
     if ((HBlinded || EBlinded) && BBlinded) /* blind w/ blindness blocked */
         you_can("see", from_what(-BLINDED)); /* Eyes of the Overworld */
+    if (Blnd_resist && !Blind) /* skip if no eyes or blindfolded */
+        you_are("not subject to light-induced blindness",
+                from_what(BLND_RES));
     if (See_invisible) {
         if (!Blind)
             enl_msg(You_, "see", "saw", " invisible", from_what(SEE_INVIS));