When reference counts were added to some string fields
the 3 true string vector fields were not duplicated as
were those other fields. Instead they were supposed to
disallow a duplicate stack reference beyond the first.
However, the actual implementation gave NULL for every
true vector field whenever such items were duplicated.
More importantly, such true string vector fields never
considered references to the shared proc_t source root
which would have forced the conversion of such vectors
into a single string form via the '_CVT' library flag.
So this commit restores the intended outcome with true
string vectors. There's only 1 valid reference allowed
and duplicates and converted fields will yield a NULL.
Signed-off-by: Jim Warner <james.warner@comcast.net>