some coordxy follow-up

Return a couple of variables that actually held a direction back
to int from coordxy.

bhit() takes int params instead of coordxy.

boomhit() takes int params instead of coordxy.

xytod() renamed to xytodir(), and takes int params (promotion will handle
coordxy params).

dtoxy(coord *, int) renamed to dirtocoord(coord *, int).

src/getpos.c

@@ -561,7 +561,7 @@ dxdy_to_dist_descr(coordxy dx, coordxy dy, boolean fulldir)
 
     if (!dx && !dy) {
         Sprintf(buf, "here");
-    } else if ((dst = xytod(dx, dy)) != -1) {
+    } else if ((dst = xytodir(dx, dy)) != -1) {
         /* explicit direction; 'one step' is implicit */
         Sprintf(buf, "%s", directionname(dst));
     } else {