cmd/pprof: print binary output in interactive mode

[hirochachacha]

Please answer these questions before submitting your issue. Thanks!

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

1. go tool pprof bin cpu.profile
2. type "pdf" then enter.
3. get random output.

What did you expect to see?

don't print binary output, create a temporal file & save to it.

What did you see instead?

binary output.

Does this issue reproduce with the latest release (go1.7.1)?

System details

go version devel +82946f1 Sun Oct 16 20:21:07 2016 +0900 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/hiro/.go"
GORACE=""
GOROOT="/Users/hiro/go"
GOTOOLDIR="/Users/hiro/go/pkg/tool/darwin_amd64"
TERM="dumb"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/wq/dwn8hs0x7njbzty9f68y61700000gn/T/go-build421080535=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
uname -v: Darwin Kernel Version 15.6.0: Mon Aug 29 20:21:34 PDT 2016; root:xnu-3248.60.11~1/RELEASE_X86_64
ProductName:    Mac OS X
ProductVersion: 10.11.6
BuildVersion:   15G1004
lldb --version: lldb-360.1.50
gdb --version: GNU gdb (GDB) 7.11.1

[gopherbot]

CL https://golang.org/cl/31123 mentions this issue.