If deriving SVN_SSH from GIT_SSH on msys, also add quotes

If deriving SVN_SSH from GIT_SSH on msys, also add quotes

In contrast to GIT_SSH, SVN_SSH requires quotes for paths that contain
spaces. As GIT_SSH will not work if it contains quotes, it is safe to
assume it never contains quotes. Also, adding quotes to SVN_SSH for paths
that do not contain spaces does no harm. So we always add quotes when
deriving SVN_SSH from GIT_SSH on msys.

This fixes msysGit issue 385, see
http://code.google.com/p/msysgit/issues/detail?id=385

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>