Fix monster hiding under hatching egg staying hidden

doc/fixes37.0

@@ -286,6 +286,7 @@ monster xorns could pass through iron bars but not eat them; monster rock
 hero poly'd into rust monster could implicitly eat bars when adjacent by
 	trying to move there, now when in rock mole form too; in xorn form
 	can explicitly eat them via 'e' after moving onto their spot
+monster hiding under an egg that hatched was kept hidden
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/timeout.c

@@ -985,6 +985,8 @@ long timeout;
             /* free egg here because we use it above */
             obj_extract_self(egg);
             obfree(egg, (struct obj *) 0);
+            if ((mon = m_at(x,y)) && !hideunder(mon) && cansee(x, y))
+                redraw = TRUE;
         }
         if (redraw)
             newsym(x, y);