[PATCH 0 of 3] Patch for issue #2134: have svn subrepos be checked out in the repo instead of cwd

[Brett Cannon]

The changesets are a patch for issue #2134: svn subrepos created
outside of cloned repos.

If you specify an svn subrepo it will be checked out in a clone in the
cwd, not the repo itself. These changesets force the svn commands used
by subrepo.py to work within the repo itself instead of cwd.

When I run the tests I do get an exception from
subprocess.Popen.__del__, but that failure existed before I touched
any code.