Create branch serf_stream_commit from trunk@28756.

The purpose of this branch is to test if we can use the new external event loop
mechanism in serf trunk to replace the current 'send delta to file before 
commit' with a streaming mechanism.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/serf_stream_commit@868831 13f79535-47bb-0310-9956-ffa450edef68