git_remote_helpers: use 2to3 if building with Python 3
git_remote_helpers: use 2to3 if building with Python 3

Using the approach detailed in the Python documentation[1], run 2to3 on
the code as part of the build if building with Python 3.

The code itself requires no changes to convert cleanly.

[1] http://docs.python.org/3.3/howto/pyporting.html#during-installation

Signed-off-by: John Keeping <a51dda7c7ff50b61eaea0444371f4a6a9301e501@keeping.me.uk>
Acked-by: Sverre Rabbelier <91e3618f486cb75969cf54d52cb06350cfe172f2@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git