doc/go1.5.txt: io.CopyBuffer and new reflect.Value handling in fmt

Change-Id: Ia0d7c2f08f8f124bcd62c7f9744227812d68903d
Reviewed-on: https://go-review.googlesource.com/8941Reviewed-by: Rob Pike <r@golang.org>

doc/go1.5.txt

@@ -29,7 +29,9 @@ database/sql: add Stats (https://golang.org/cl/7950)
 encoding/base64: add unpadded encodings (https://golang.org/cl/1511)
 flag: new nicer format for PrintDefaults (https://golang.org/cl/7330)
 fmt: empty slices now print nothing with %x (bug fix) (https://golang.org/cl/8864)
+fmt: reflect.Value now prints what it holds (https://golang.org/cl/8731)
 go/ast: add Implicit field to ast.EmptyStmt; changed meaning of ast.EmptyStmt.Semicolon position (https://golang.org/cl/5720)
+io: add CopyBuffer, Copy with user-provided buffer (https://golang.org/cl/8730)
 log: add SetOutput functions (https://golang.org/cl/2686, https://golang.org/cl/3023)
 log: add LUTC flag (https://golang.org/cl/8761)
 math/big: add arbitrary precision Floats (many cl's)