spec: fix typo

Fixes #10893.

Change-Id: I8afeb55acda1e1c8e181379dbaf443716d63ded1
Reviewed-on: https://go-review.googlesource.com/10201Reviewed-by: Rob Pike <r@golang.org>

doc/go_spec.html

 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of April 22, 2015",
+	"Subtitle": "Version of May 18, 2015",
 	"Path": "/ref/spec"
 }-->
 
@@ -2605,7 +2605,7 @@ one may write:
 <pre>
 t.z          // t.z
 t.y          // t.T1.y
-t.x          // (*t.TO).x
+t.x          // (*t.T0).x
 
 p.z          // (*p).z
 p.y          // (*p).T1.y