spec: we're now at Unicode 6.2.0

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6812060

doc/go_spec.html

 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of October 19, 2012",
+	"Subtitle": "Version of October 31, 2012",
 	"Path": "/ref/spec"
 }-->
 
@@ -118,7 +118,7 @@ unicode_digit  = /* a Unicode code point classified as "Decimal Digit" */ .
 </pre>
 
 <p>
-In <a href="http://www.unicode.org/versions/Unicode6.0.0/">The Unicode Standard 6.0</a>,
+In <a href="http://www.unicode.org/versions/Unicode6.2.0/">The Unicode Standard 6.2</a>,
 Section 4.5 "General Category"
 defines a set of character categories.  Go treats
 those characters in category Lu, Ll, Lt, Lm, or Lo as Unicode letters,