vsdg: introduce copy method declaration for jive_value_type
vsdg: introduce copy method declaration for jive_value_type

Introduce copy method for jive_value_type to avoid warnings.

Signed-off-by: Helge Bahmann <c5618920f622561f9c0ec5c42219c4c08180149f@chaoticmind.net>

phate/jive,phate/jive,phate/jive