Need to set sf->save_to_dir from value of s2d, or else saving .sfdir
to .sfd will save as directory.
Merge pull request #403 from blipvert/fixes/7

Need to set sf->save_to_dir from value of s2d, or else saving .sfdir to .sfd will save as directory.
Merge pull request #405 from JoesCat/master

resolved issue #401