GLOBAL MARKETS-Shares gain on U.S. tech earnings, ECB purchase plans

* Wall Street higher on Apple, Texas Instruments results * European shares surge on report ECB to buy corporate bonds * US Treasury prices, euro fall * China GDP data weighs on Chinese shares (Adds U.S. market open; changes byline, dateline; previous LONDON) By Sam Forgione NEW YORK, Oct 21 (Reuters) - A measure of global equity markets advanced on Tuesday after technology earnings lifted U.S. shares and the prospect of European Central Bank corporate bond purchases boosted