Draft for carray module in Rust

Incomplete support for sqlite3_bind_pointer.
Make Context::set_result return a Result.
Add Values::get_array.

src/vtab/series.rs

@@ -255,8 +255,7 @@ impl VTabCursor for SeriesTabCursor {
             SERIES_COLUMN_STEP => self.step,
             _ => self.value,
         };
-        ctx.set_result(&x);
-        Ok(())
+        ctx.set_result(&x)
     }
     fn rowid(&self) -> Result<i64> {
         Ok(self.row_id)