Add support for limited mode without unsafe pkg.

This commit adds support for compiling spew without the unsafe package.
When compiled without the unsafe package, some of the more advanced
features such as invoking stringers on pointers from non-pointer
variables and unexported struct fields are not available.

By default, spew will be compiled in the limited mode for Google App
Engine since the unsafe package is not available there.  Additionally,
spew can be compiled without the unsafe package manually by specifying
the "disableunsafe" build tag.

Finally, a new package-level constant named "UnsafeDisabled" has been
exposed which can be used to programmatically determine if spew was
compiled with access to the unsafe package.

1 files changed, 3 insertions, 7 deletions

diff --git a/spew/example_test.go b/spew/example_test.go
index a7acd14..de6c4e3 100644
--- a/spew/example_test.go
+++ b/spew/example_test.go
@@ -18,6 +18,7 @@ package spew_test
 
 import (
 	"fmt"
+
 	"github.com/davecgh/go-spew/spew"
 )
 
@@ -41,7 +42,6 @@ func (f Flag) String() string {
 }
 
 type Bar struct {
-	flag Flag
 	data uintptr
 }
 
@@ -74,7 +74,6 @@ func ExampleDump() {
 		}
 
 		type Bar struct {
-			flag Flag
 			data uintptr
 		}
 
@@ -85,7 +84,7 @@ func ExampleDump() {
 	*/
 
 	// Setup some sample data structures for the example.
-	bar := Bar{Flag(flagTwo), uintptr(0)}
+	bar := Bar{uintptr(0)}
 	s1 := Foo{bar, map[interface{}]interface{}{"one": true}}
 	f := Flag(5)
 	b := []byte{
@@ -102,7 +101,6 @@ func ExampleDump() {
 	// Output:
 	// (spew_test.Foo) {
 	//  unexportedField: (spew_test.Bar) {
-	//   flag: (spew_test.Flag) flagTwo,
 	//   data: (uintptr) <nil>
 	//  },
 	//  ExportedField: (map[interface {}]interface {}) (len=1) {
@@ -172,7 +170,7 @@ func ExampleConfigState_Dump() {
 	scs2 := spew.ConfigState{Indent: " "}
 
 	// Setup some sample data structures for the example.
-	bar := Bar{Flag(flagTwo), uintptr(0)}
+	bar := Bar{uintptr(0)}
 	s1 := Foo{bar, map[interface{}]interface{}{"one": true}}
 
 	// Dump using the ConfigState instances.
@@ -182,7 +180,6 @@ func ExampleConfigState_Dump() {
 	// Output:
 	// (spew_test.Foo) {
 	// 	unexportedField: (spew_test.Bar) {
-	// 		flag: (spew_test.Flag) flagTwo,
 	// 		data: (uintptr) <nil>
 	// 	},
 	// 	ExportedField: (map[interface {}]interface {}) (len=1) {
@@ -191,7 +188,6 @@ func ExampleConfigState_Dump() {
 	// }
 	// (spew_test.Foo) {
 	//  unexportedField: (spew_test.Bar) {
-	//   flag: (spew_test.Flag) flagTwo,
 	//   data: (uintptr) <nil>
 	//  },
 	//  ExportedField: (map[interface {}]interface {}) (len=1) {