Log Message:
Update to 1.3116

Upstream changes:
[ ENHANCEMENTS ]
    * GH #767: forwarded_for_address() now looks for HTTP_X_FORWARDED_FOR if
        X_FORWARDED_FOR is not there. (Jakob Voss)
    * GH #936: Add file locking to file logger. (David Golden)
    * GH #937: Add details to tutorial. (Craig Treptow)