Multiple Updates from Rust Core links wrong in 149

[b-jonas0]

In the This Week in Rust 149 document at "https://this-week-in-rust.org/blog/2016/09/27/this-week-in-rust-149/", in the section "Updates from Rust Core", some of the updates mentioned are a link to the wrong target.

• "TypedArena now allocates lazily" should link to Lazily allocate TypedArena's first chunk rust#36592
• "RBML is gone" should link to Refactor away RBML from rustc_metadata.  rust#36551

The current link targets are definitely wrong, because they are equal to the target of a previous link, but I'm not completely certain I identified the correct targets here, so please check that.

[nasa42]

Fixed now, thanks!