Fix Windows command-line argument quoting in the Python test harness. Arguments ending with a backslash were not correctly quoted, among other issues.  This reverts r875257.
Fix Windows command-line argument quoting in the Python test harness.
Arguments ending with a backslash were not correctly quoted, among other
issues.  This reverts r875257.

* subversion/tests/cmdline/svntest/main.py
  (_quote_arg): Do the quoting more correctly, using subprocess.list2cmdline()
    on Windows and in-line code on Unix.
  (open_pipe): Pass the list of arguments directly to subprocess.Popen()
    instead of trying to quote it ourselves on Windows.  Use our own quoting
    only for display purposes.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion