change the type of xytod()'s return value to int

xytod()'s return value is an index, so its type should be int, not coordxy.

src/cmd.c

@@ -3604,7 +3604,7 @@ rhack(int key)
 }
 
 /* convert an x,y pair into a direction code */
-coordxy
+int
 xytod(coordxy x, coordxy y)
 {
     int dd;