Problem: getregionpos() doesn't handle one char selection.
Solution: Handle startspaces differently when is_oneChar is set.
Also add a test for an exclusive charwise selection with
multibyte chars (zeertzjq)
closes: #14825
Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>