go1.4: add note about change to bufio.SplitFunc at EOF

CC=golang-codereviews
https://golang.org/cl/159800044

doc/go1.4.txt

@@ -20,6 +20,7 @@ cmd/go: compile and link all _test.go files during 'go test', even in packages w
 cmd/go: (via go/build): a GOOS prefix acts as a tag only if preceded by an underscore. this is a breaking change. (CL 147690043)
 
 asm: make textflag.h available outside of cmd/ld (CL 128050043)
+bufio: handling of empty tokens at EOF changed, may require scanner change (CL 145390043)
 crypto/tls: add support for ALPN (RFC 7301) (CL 108710046)
 crypto/tls: support programmatic selection of server certificates (CL 107400043)
 fmt: print type *map[T]T as &map[k:v] (CL 154870043)