Allow "+" to remain unescaped by csprintf('%R', ...)
Ref T10923. Currently, when we %R ("readable") escape SVN SSH URIs (svn+ssh://...), they get quoted because they contain a +.
However, they don't need to be quoted, since + is not a special character in the shell.
- Added and ran test cases.
- Viewed SVN in Diffusion, saw unquoted checkout URI.
Reviewed By: chad
Maniphest Tasks: T10923
Differential Revision: https://secure.phabricator.com/D15882