WASHINGTON (Reuters) - Russia is likely to maintain a big presence in Syria despite Russian President Vladimir Putin s announcement of a partial military withdrawal, the U.S. special envoy to the coalition fighting the Islamic State insurgent group said on Friday.  I ve seen the announcement that they ... are going to withdraw from Syria, but that remains to be seen,  U.S. envoy Brett McGurk told reporters.  I think they will retain a fairly significant presence.  