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/timeout.c

@@ -79,6 +79,7 @@ static const struct propname {
     { SICK_RES, "sickness resistance" },
     { ANTIMAGIC, "magic resistance" },
     { HALLUC_RES, "hallucination resistance" },
+    { BLND_RES, "light-induced blindness resistance" },
     { FUMBLING, "fumbling" },
     { HUNGER, "voracious hunger" },
     { TELEPAT, "telepathic" },