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/database/sql/ctxutil.go

@@ -0,0 +1,163 @@
+// Copyright 2016 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 sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+)
+
+func ctxDriverPrepare(ctx context.Context, ci driver.Conn, query string) (driver.Stmt, error) {
+	if ciCtx, is := ci.(driver.ConnPrepareContext); is {
+		return ciCtx.PrepareContext(ctx, query)
+	}
+	si, err := ci.Prepare(query)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			si.Close()
+			return nil, ctx.Err()
+		}
+	}
+	return si, err
+}
+
+func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, nvdargs []driver.NamedValue) (driver.Result, error) {
+	if execerCtx, is := execer.(driver.ExecerContext); is {
+		return execerCtx.ExecContext(ctx, query, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	resi, err := execer.Exec(query, dargs)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			return resi, ctx.Err()
+		}
+	}
+	return resi, err
+}
+
+func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, nvdargs []driver.NamedValue) (driver.Rows, error) {
+	if queryerCtx, is := queryer.(driver.QueryerContext); is {
+		ret, err := queryerCtx.QueryContext(ctx, query, nvdargs)
+		return ret, err
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	rowsi, err := queryer.Query(query, dargs)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			rowsi.Close()
+			return nil, ctx.Err()
+		}
+	}
+	return rowsi, err
+}
+
+func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Result, error) {
+	if siCtx, is := si.(driver.StmtExecContext); is {
+		return siCtx.ExecContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	resi, err := si.Exec(dargs)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			return resi, ctx.Err()
+		}
+	}
+	return resi, err
+}
+
+func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Rows, error) {
+	if siCtx, is := si.(driver.StmtQueryContext); is {
+		return siCtx.QueryContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	rowsi, err := si.Query(dargs)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			rowsi.Close()
+			return nil, ctx.Err()
+		}
+	}
+	return rowsi, err
+}
+
+var errLevelNotSupported = errors.New("sql: selected isolation level is not supported")
+
+func ctxDriverBegin(ctx context.Context, opts *TxOptions, ci driver.Conn) (driver.Tx, error) {
+	if ciCtx, is := ci.(driver.ConnBeginTx); is {
+		dopts := driver.TxOptions{}
+		if opts != nil {
+			dopts.Isolation = driver.IsolationLevel(opts.Isolation)
+			dopts.ReadOnly = opts.ReadOnly
+		}
+		return ciCtx.BeginTx(ctx, dopts)
+	}
+
+	if ctx.Done() == context.Background().Done() {
+		return ci.Begin()
+	}
+
+	if opts != nil {
+		// Check the transaction level. If the transaction level is non-default
+		// then return an error here as the BeginTx driver value is not supported.
+		if opts.Isolation != LevelDefault {
+			return nil, errors.New("sql: driver does not support non-default isolation level")
+		}
+
+		// If a read-only transaction is requested return an error as the
+		// BeginTx driver value is not supported.
+		if opts.ReadOnly {
+			return nil, errors.New("sql: driver does not support read-only transactions")
+		}
+	}
+
+	txi, err := ci.Begin()
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			txi.Rollback()
+			return nil, ctx.Err()
+		}
+	}
+	return txi, err
+}
+
+func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
+	dargs := make([]driver.Value, len(named))
+	for n, param := range named {
+		if len(param.Name) > 0 {
+			return nil, errors.New("sql: driver does not support the use of Named Parameters")
+		}
+		dargs[n] = param.Value
+	}
+	return dargs, nil
+}