Add the benchmark script and utilities used for repository performance
testing to our dev tools section.  Most of them are Windows-sepecifc.

* tools/dev/benchmarks/RepoPerf
  New folder.

* tools/dev/benchmarks/RepoPerf/ClearMemory.cpp
  (): New file.  Trivial "RAM cleaner" for Windows.

* tools/dev/benchmarks/RepoPerf/copy_repo.py
  (): New file.  Generic tool to multiply repositories and to create
      realistic on-disk data layouts.

* tools/dev/benchmarks/RepoPerf/TimeWin.cpp
  (): New file.  Windows tool measuring execution time and CPU usage
      of a given command while suppressing its output.

* tools/dev/benchmarks/RepoPerf/win_repo_bench.py
  (): New file.  The benchmarking script I used on Windows.  It is
      currently quite inflexible (paths etc. are hard-coded).

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1610264 13f79535-47bb-0310-9956-ffa450edef68