Make SINKS unconditional.

src/mthrowu.c

@@ -431,11 +431,8 @@ struct obj *obj;		/* missile (or stack providing it) */
 			/* missile might hit iron bars */
 			|| (levl[bhitpos.x+dx][bhitpos.y+dy].typ == IRONBARS &&
 			hits_bars(&singleobj, bhitpos.x, bhitpos.y, !rn2(5), 0))
-#ifdef SINKS
 			/* Thrown objects "sink" */
-			|| IS_SINK(levl[bhitpos.x][bhitpos.y].typ)
-#endif
-								) {
+			|| IS_SINK(levl[bhitpos.x][bhitpos.y].typ)) {
 		    if (singleobj) /* hits_bars might have destroyed it */
 			(void) drop_throw(singleobj, 0, bhitpos.x, bhitpos.y);
 		    break;