Add tracking issue number for `seek_convenience`
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 4c88fc8..7147b64 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -1381,7 +1381,7 @@
     ///     Ok(())
     /// }
     /// ```
-    #[unstable(feature = "seek_convenience", issue = "0")]
+    #[unstable(feature = "seek_convenience", issue = "59359")]
     fn stream_len(&mut self) -> Result<u64> {
         let old_pos = self.stream_position()?;
         let len = self.seek(SeekFrom::End(0))?;
@@ -1420,7 +1420,7 @@
     ///     Ok(())
     /// }
     /// ```
-    #[unstable(feature = "seek_convenience", issue = "0")]
+    #[unstable(feature = "seek_convenience", issue = "59359")]
     fn stream_position(&mut self) -> Result<u64> {
         self.seek(SeekFrom::Current(0))
     }