Merge the 1.8.x-issue4707 branch:

 * r1816069,1816106
   Issue #4707: svnrdump dump: 2GB limit on content-length header.
   Justification:
     Large file support is broken in svnrdump <= 1.8.
   Notes:
     Only <= 1.8.x was broken; 1.9.x uses refactored code without the bug.
     Ideally we'd add a regression test; I'll leave that decision to reviewers.
   Branch:
     1.8.x-issue4707
   Votes:
     +1: julianfoad, luke1410, rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1816207 13f79535-47bb-0310-9956-ffa450edef68