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 ForgioneNEW YORK, Oct 21 (Reuters) - A measure of global equity markets advanced on Tuesday after technology earnings lifted U.S. shares an