By Joe Cash BEIJING (Reuters) -China's manufacturing activity shrank for a sixth month in September, an official survey showed on Tuesday, suggesting producers are waiting for further stimulus to boost domestic demand, as well as clarity on a U.S. trade deal. The official purchasing managers' index (PMI) rose to a six-month high of 49.8 in September versus 49.4 in August. It remained below the 50-mark separating growth from contraction, but topped a median forecast of 49.6 in a Reuters poll. The prolong ...