[thin_dump (rust)] First pass at thin_dump.

Doesn't include --repair.

This includes <def> and <ref> sections for shared regions.

tests/thin_shrink.rs

@@ -103,6 +103,14 @@ impl<'a, V: ThinVisitor> xml::MetadataVisitor for ThinXmlVisitor<'a, V> {
         Ok(Visit::Continue)
     }
 
+    fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
+        todo!();
+    }
+
+    fn def_shared_e(&mut self) -> Result<Visit> {
+        todo!();
+    }
+
     fn device_b(&mut self, d: &xml::Device) -> Result<Visit> {
         self.thin_id = Some(d.dev_id);
         Ok(Visit::Continue)
@@ -125,6 +133,10 @@ impl<'a, V: ThinVisitor> xml::MetadataVisitor for ThinXmlVisitor<'a, V> {
         Ok(Visit::Continue)
     }
 
+    fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
+        todo!();
+    }
+
     fn eof(&mut self) -> Result<Visit> {
         Ok(Visit::Stop)
     }