US STOCKS-Wall St set to open lower as China, Wal-Mart weigh
* Wal-Mart falls after cutting full-year forecast
* Chinese stock slumps, yuan devaluations fears resurface
* Oil prices, copper near six-year lows
* July housing starts beat expectations; at nearly 8-year high
* Home Depot, TJX rise after results
* Futures down: Dow 56 pts, S&P 5 pts, Nasdaq 13 pts (Adds details, comment, updates prices)
By Tanya Agrawal
Aug 18 (Reuters) - Wall Street was set to open lower on Tuesday, weighed down by a 6 percent slump in Chinese shares and disappointing results from Wal-Mart.
Wal-Mart shares fell 2.6 percent to $70.05 in premarket trading after the Dow component reported weaker-than-expected quarterly earnings and lowered its full-year forecast. The stock was the biggest loser on the Dow Jones industrial average. Continuación...