libgo: update to Go1.10rc1

    
    Reviewed-on: https://go-review.googlesource.com/90295

From-SVN: r257127

libgo/go/cmd/go/testdata/src/coverdot1/p.go

+package coverdot1
+
+func F() {}

libgo/go/cmd/go/testdata/src/coverdot2/p.go

+package coverdot2
+
+import . "coverdot1"
+
+func G() { F() }

libgo/go/cmd/go/testdata/src/coverdot2/p_test.go

+package coverdot2
+
+import "testing"
+
+func TestG(t *testing.T) {
+	G()
+}

libgo/go/runtime/testdata/testprog/badtraceback.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"runtime"
+	"runtime/debug"
+	"unsafe"
+)
+
+func init() {
+	register("BadTraceback", BadTraceback)
+}
+
+func BadTraceback() {
+	// Disable GC to prevent traceback at unexpected time.
+	debug.SetGCPercent(-1)
+
+	// Run badLR1 on its own stack to minimize the stack size and
+	// exercise the stack bounds logic in the hex dump.
+	go badLR1()
+	select {}
+}
+
+//go:noinline
+func badLR1() {
+	// We need two frames on LR machines because we'll smash this
+	// frame's saved LR.
+	badLR2(0)
+}
+
+//go:noinline
+func badLR2(arg int) {
+	// Smash the return PC or saved LR.
+	lrOff := unsafe.Sizeof(uintptr(0))
+	if runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" {
+		lrOff = 32 // FIXED_FRAME or sys.MinFrameSize
+	}
+	lrPtr := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&arg)) - lrOff))
+	*lrPtr = 0xbad
+
+	// Print a backtrace. This should include diagnostics for the
+	// bad return PC and a hex dump.
+	panic("backtrace")
+}