Add wrapper str_list_make_v3() to replace the old S3 behavior of

Add wrapper str_list_make_v3() to replace the old S3 behavior of
str_list_make(). From Dan Sledz <dan.sledz@isilon.com>:
In samba 3.2 passing NULL or an empty string returned NULL.
In master, it now returns a list of length 1 with the first string set
to NULL (an empty list).
Jeremy.