Wireshark-dev: [Wireshark-dev] VALS() with populated "unknown string"

Date: Mon, 16 Sep 2013 06:49:07 -0400 (EDT)
Is there a way to provide the "unknown string" for the val_to_str call made in hf_ registration (ie some derivation of the VALS() macro)?   There are many proto_tree_add_[u]int_format[_value] calls that are done strictly to provided an "unknown string" for the val_to_str that is different than the default of "Unknown".  If there was such a way, many of these calls could be converted to proto_tree_add_item or proto_tree_add_[u]int.
 
If there isn't such a thing, how easy/hard would it be to implement?