Function dwg_dynapi_header_value 

pub unsafe extern "C" fn dwg_dynapi_header_value(
    dwg: *const Dwg_Data,
    fieldname: *const c_char,
    out: *mut c_void,
    fp: *mut Dwg_DYNAPI_field,
) -> bool

Returns the HEADER.fieldname value in out. The optional Dwg_DYNAPI_field *fp is filled with the field types from dynapi.c