Fix to transpile.js for indexOf
Fix to transpile.js for indexOf

Fix to transpile.js for indexOf()->mb_strpos() for PHP transpile -- no match returns -1 in JS, but false in PHP.

Affects only bitstamp->get_currency_id_from_transaction() and delta->fetch_markets() PHP methods, fixing bugs in both.
ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt