Speeding up Scanless interface: t+
Speeding up Scanless interface: t+
Ensure child objects increment ref count of base grammar SV: t+

When data in a base grammar was used in a child, the Libmarpa
grammar had its reference count incremented properly, but the
SV did *not*.  It was possible that the grammar "wrapper" might
be freed and overwritten before the child object and that the
child object might use it.  (Main use was the throw setting.)
This potential issue is now corrected.