Takes a define xml and pulls out the value level metadata including codelist_id's, defines_id's, and where clause. There is one row per variable expect when there is a where clause, at which point there is one row per value.
xml_to_value_spec(doc)xml document
tibble with the value level information
Other xml builder:
xml_to_codelist(),
xml_to_derivations(),
xml_to_ds_spec(),
xml_to_ds_vars(),
xml_to_var_spec()