FOREX-U.S. dollar mixed after upbeat data; Aussie and Kiwi jump

* U.S. existing home sales data in May stronger-than-expected * HSBC China PMI rises to 50.8 in June from 49.4 in May * Canadian dollar extends gains after inflation shock NEW YORK, June 23 (Reuters) - Optimism over China's economic prospects drove the Australian, New Zealand and Canadian dollars higher on Monday, while the euro struggled to make headway after some softer business- sentiment ...