(vc-svn-dired-state-info): Use `added' for added files and

(vc-svn-dired-state-info): Use `added' for added files and
don't use `concat' unnecessarily.  Remove impossible cases.
(vc-svn-register, vc-svn-find-version, vc-svn-diff-tree):
Use vc-switches.
(vc-svn-checkin): Use vc-switches.  Fix up regexp.
(vc-svn-diff): Use vc-switches.
Don't return 0 for newly added empty files.
Don't use svn's return status.
(vc-svn-parse-status): Recognize copied files as well.
Use the last-modified revision for workfile-version.