Auto merge of #26579 - Techern:start-12-doc, r=brson

At the moment, it only mentions the fix to parallel codegen.

I was going to add more, but I have to go for a while - If this isn't reviewed when I get back, I'll remove it and resubmit it after filling in more :)

Author: bors

RELEASES.md

@@ -1,3 +1,18 @@
+Version 1.2.0 (August 2015)
+===========================
+
+Highlights
+----------
+
+* [Parallel codegen][parcodegen] is now working again, which can substantially
+  speed up large builds in debug mode; It also gets another ~33% speedup when
+  bootstrapping on a 4 core machine (using 8 jobs). It's not enabled by default,
+  but will be "in the near future"
+
+
+[parcodegen]: https://github.com/rust-lang/rust/pull/26018
+
+
 Version 1.1.0 (June 2015)
 =========================