Integer types cleanup

Try to be a bit more strict about integer types, use off_t or int64_t for
file size and file offsets.

Replace safe_ato*() by safe_atoi32() and safe_atoi64(), fix integer types
at call sites to match.

src/httpd_dacp.c

@@ -262,7 +262,7 @@ dacp_reply_playstatusupdate(struct evhttp_request *req, struct evbuffer *evbuf,
       return;
     }
 
-  ret = safe_atoi(param, &reqd_rev);
+  ret = safe_atoi32(param, &reqd_rev);
   if (ret < 0)
     {
       DPRINTF(E_LOG, L_DACP, "Parameter revision-number not an integer\n");