git-svn: fix cloning of HTTP URLs with '+' in their path
With this, git svn clone -s http://svn.gnome.org/svn/gtk+
is successful.
Also modified the funky rename test for this, which _does_
include escaped '+' signs for HTTP URLs. SVN seems to accept
either "+" or "%2B" in filenames and directories (just not the
main URL), so I'll leave it alone for now.
Signed-off-by: Eric Wong <normalperson@yhbt.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>