doc/go1.5: mention the change in certificate wildcard handling.

https://go-review.googlesource.com/#/c/5691/ shouldn't affect anyone
because it reflects the RFC and behaviour of modern browsers, but it's
probably worth mentioning.

Change-Id: I8a8eedaac5226b1d8018dc56de6b2d41bd82a642
Reviewed-on: https://go-review.googlesource.com/5862Reviewed-by: Rob Pike <r@golang.org>

doc/go1.5.txt

@@ -11,6 +11,7 @@ bufio: add Reader.Discard (https://golang.org/cl/2260)
 crypto/cipher: clarify what will happen if len(src) != len(dst) for the Stream interface. (https://golang.org/cl/1754)
 crypto/elliptic: add Name field to CurveParams struct (https://golang.org/cl/2133)
 crypto/tls: change default minimum version to TLS 1.0. (https://golang.org/cl/1791)
+crypto/x509: wildcards are now only accepted as the first label (https://golang.org/cl/5691)
 encoding/base64: add unpadded encodings (https://golang.org/cl/1511)
 go/ast: add Implicit field to ast.EmptyStmt; changed meaning of ast.EmptyStmt.Semicolon position (https://golang.org/cl/5720)
 log: add SetOutput functions (https://golang.org/cl/2686, https://golang.org/cl/3023)