libgo: update to Go 1.8 release candidate 1

Compiler changes:
      * Change map assignment to use mapassign and assign value directly.
      * Change string iteration to use decoderune, faster for ASCII strings.
      * Change makeslice to take int, and use makeslice64 for larger values.
      * Add new noverflow field to hmap struct used for maps.
    
    Unresolved problems, to be fixed later:
      * Commented out test in go/types/sizes_test.go that doesn't compile.
      * Commented out reflect.TestStructOf test for padding after zero-sized field.
    
    Reviewed-on: https://go-review.googlesource.com/35231

gotools/:
	Updates for Go 1.8rc1.
	* Makefile.am (go_cmd_go_files): Add bug.go.
	(s-zdefaultcc): Write defaultPkgConfig.
	* Makefile.in: Rebuild.

From-SVN: r244456

libgo/go/sort/sort.go

@@ -2,10 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate go run genzfunc.go
+
 // Package sort provides primitives for sorting slices and user-defined
 // collections.
 package sort
 
+import "reflect"
+
 // A type, typically a collection, that satisfies sort.Interface can be
 // sorted by the routines in this package. The methods require that the
 // elements of the collection be enumerated by an integer index.
@@ -212,14 +216,63 @@ func quickSort(data Interface, a, b, maxDepth int) {
 // It makes one call to data.Len to determine n, and O(n*log(n)) calls to
 // data.Less and data.Swap. The sort is not guaranteed to be stable.
 func Sort(data Interface) {
-	// Switch to heapsort if depth of 2*ceil(lg(n+1)) is reached.
 	n := data.Len()
-	maxDepth := 0
+	quickSort(data, 0, n, maxDepth(n))
+}
+
+// maxDepth returns a threshold at which quicksort should switch
+// to heapsort. It returns 2*ceil(lg(n+1)).
+func maxDepth(n int) int {
+	var depth int
 	for i := n; i > 0; i >>= 1 {
-		maxDepth++
+		depth++
 	}
-	maxDepth *= 2
-	quickSort(data, 0, n, maxDepth)
+	return depth * 2
+}
+
+// lessSwap is a pair of Less and Swap function for use with the
+// auto-generated func-optimized variant of sort.go in
+// zfuncversion.go.
+type lessSwap struct {
+	Less func(i, j int) bool
+	Swap func(i, j int)
+}
+
+// Slice sorts the provided slice given the provided less function.
+//
+// The sort is not guaranteed to be stable. For a stable sort, use
+// SliceStable.
+//
+// The function panics if the provided interface is not a slice.
+func Slice(slice interface{}, less func(i, j int) bool) {
+	rv := reflect.ValueOf(slice)
+	swap := reflect.Swapper(slice)
+	length := rv.Len()
+	quickSort_func(lessSwap{less, swap}, 0, length, maxDepth(length))
+}
+
+// SliceStable sorts the provided slice given the provided less
+// function while keeping the original order of equal elements.
+//
+// The function panics if the provided interface is not a slice.
+func SliceStable(slice interface{}, less func(i, j int) bool) {
+	rv := reflect.ValueOf(slice)
+	swap := reflect.Swapper(slice)
+	stable_func(lessSwap{less, swap}, rv.Len())
+}
+
+// SliceIsSorted tests whether a slice is sorted.
+//
+// The function panics if the provided interface is not a slice.
+func SliceIsSorted(slice interface{}, less func(i, j int) bool) bool {
+	rv := reflect.ValueOf(slice)
+	n := rv.Len()
+	for i := n - 1; i > 0; i-- {
+		if less(i, i-1) {
+			return false
+		}
+	}
+	return true
 }
 
 type reverse struct {
@@ -337,7 +390,10 @@ func StringsAreSorted(a []string) bool { return IsSorted(StringSlice(a)) }
 // It makes one call to data.Len to determine n, O(n*log(n)) calls to
 // data.Less and O(n*log(n)*log(n)) calls to data.Swap.
 func Stable(data Interface) {
-	n := data.Len()
+	stable(data, data.Len())
+}
+
+func stable(data Interface, n int) {
 	blockSize := 20 // must be > 0
 	a, b := 0, blockSize
 	for b <= n {