Deliver WiredTiger event notifications (messages, errors, progress) into Erlang for logging

WiredTiger will log to std{err,out} informational messages, error messages and progress messages unless you provide proper call back functions.  This set of patches provide a set of call backs to WiredTiger which take the messages and send them to a waiting gen_server which then sends them on to lager for logging along with other messages from Riak.