bundle the display-related hints, that tell bot() and others

that an update is required, into a struct. Remove it from
context since there is no reason to save those.

src/explode.c

@@ -630,7 +630,7 @@ explode(
                 u.mh -= damu;
             else
                 u.uhp -= damu;
-            gc.context.botl = 1;
+            display.botl = 1;
         }
 
         /* You resisted the damage, lets not keep that to ourselves */