Merge the r1488294 group from trunk:

 * r1488294, r1489935
   Add signal information to external program errors.
   Justification:
     Makes it easier to diagnose failures.
   Votes:
     +1: philip, danielsh (without r1489935)
     +1: rhuijben, stefan2


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1490325 13f79535-47bb-0310-9956-ffa450edef68