Remove vtab() function from VTabCursor trait

src/vtab/csvtab.rs

@@ -272,15 +272,16 @@ impl CSVTabCursor {
             eof: false,
         }
     }
+
+    /// Accessor to the associated virtual table.
+    fn vtab(&self) -> &CSVTab {
+        unsafe { &*(self.base.pVtab as *const CSVTab) }
+    }
 }
 
 impl VTabCursor for CSVTabCursor {
     type Table = CSVTab;
 
-    fn vtab(&self) -> &CSVTab {
-        unsafe { &*(self.base.pVtab as *const CSVTab) }
-    }
-
     // Only a full table scan is supported.  So `filter` simply rewinds to
     // the beginning.
     fn filter(&mut self, _idx_num: c_int, _idx_str: Option<&str>, _args: &Values) -> Result<()> {