Fix vs 2015 compile issue.
Fix vs 2015 compile issue.

nekulin/arangodb,nekulin/arangodb,nvoron23/arangodb,nekulin/arangodb,nekulin/arangodb,nekulin/arangodb,nvoron23/arangodb,nvoron23/arangodb,nvoron23/arangodb,nvoron23/arangodb,nekulin/arangodb,nekulin/arangodb,nvoron23/arangodb,nekulin/arangodb,nekulin/arangodb,nekulin/arangodb,nvoron23/arangodb,nvoron23/arangodb,nvoron23/arangodb,nvoron23/arangodb