Fix iter_svn_log_entries ancestry-handling problems

Fix iter_svn_log_entries ancestry-handling problems

Change return format of find_svn_ancestors() to include
copyfrom_path+copyfrom_rev info.  We need this in iter_svn_log_entries()
for correctly "svn log"'ing over only valid ancestry. Previously, we
were basically assuming that copyfrom_rev was always revision-1, and
trying to "svn log" on that revision-range can yield errors.

* svn2svn/run/svn2svn.py (find_svn_ancestors): Change return format
so that each entry in the array is a path+revision+copyfrom_path+copyfrom_rev
tuplet.
* svn2svn/run/svn2svn.py (do_svn_add): Minor changes to support new
find_svn_ancestors() return format.

* svn2svn/run/svn2svn.py (do_svn_add_dir): Fix local-not-remote
handling, to correctly handling directories.