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/os/env_unix_test.go

@@ -7,6 +7,7 @@
 package os_test
 
 import (
+	"fmt"
 	. "os"
 	"testing"
 )
@@ -28,3 +29,28 @@ func TestSetenvUnixEinval(t *testing.T) {
 		}
 	}
 }
+
+var shellSpecialVarTests = []struct {
+	k, v string
+}{
+	{"*", "asterisk"},
+	{"#", "pound"},
+	{"$", "dollar"},
+	{"@", "at"},
+	{"!", "exclamation mark"},
+	{"?", "question mark"},
+	{"-", "dash"},
+}
+
+func TestExpandEnvShellSpecialVar(t *testing.T) {
+	for _, tt := range shellSpecialVarTests {
+		Setenv(tt.k, tt.v)
+		defer Unsetenv(tt.k)
+
+		argRaw := fmt.Sprintf("$%s", tt.k)
+		argWithBrace := fmt.Sprintf("${%s}", tt.k)
+		if gotRaw, gotBrace := ExpandEnv(argRaw), ExpandEnv(argWithBrace); gotRaw != gotBrace {
+			t.Errorf("ExpandEnv(%q) = %q, ExpandEnv(%q) = %q; expect them to be equal", argRaw, gotRaw, argWithBrace, gotBrace)
+		}
+	}
+}