doc: correct the number of changes to the language in go1.8.html

And link it.

Change-Id: Ic0105468435299fb1638f86522f4f3ce417ec1c2
Reviewed-on: https://go-review.googlesource.com/33871Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.8.html

@@ -25,7 +25,7 @@ release notes. Go 1.8 is expected to be released in February 2017.
 <p>
 The latest Go release, version 1.8, arrives six months after <a href="go1.7">Go 1.7</a>.
 Most of its changes are in the implementation of the toolchain, runtime, and libraries.
-There is one minor change to the language specification.
+There are <a href="#language">two minor changes</a> to the language specification.
 As always, the release maintains the Go 1 <a href="/doc/go1compat.html">promise of compatibility</a>.
 We expect almost all Go programs to continue to compile and run as before.
 </p>