Auto merge of #27860 - m4rw3r:rustdoc_unstable_feature_issue, r=alexcrichton

Implemented #27759 

Example:

![screen shot 2015-08-16 at 21 45 17](https://cloud.githubusercontent.com/assets/108100/9295040/1fb24d50-4460-11e5-8ab8-81ac5330974a.png)

1 files changed, 2 insertions, 1 deletions

diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index e226e9fa154..f05ef0fe5da 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -58,7 +58,8 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
-       html_playground_url = "https://play.rust-lang.org/")]
+       html_playground_url = "https://play.rust-lang.org/",
+       issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![doc(test(no_crate_inject))]
 
 #![no_core]