Merge the r1568953 group from trunk:

 * r1568953, r1568955
   Ensure that access to the FSFS transaction list and free transaction pointer
   is properly synchronized on Windows.
   Justification:
     Possible memory corruption in multi-threaded server on Windows. Regression
     from 1.7.x.
   Votes:
     +1: ivan, rhuijben, philip


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1569626 13f79535-47bb-0310-9956-ffa450edef68