add a debugging printer to the gob package.
used only for debugging, debug.go is not normally part of the package source.

also add a dump program to call it.

R=rsc
CC=golang-dev
https://golang.org/cl/183075
diff --git a/src/pkg/gob/dump.go b/src/pkg/gob/dump.go
new file mode 100644
index 0000000..a055105
--- /dev/null
+++ b/src/pkg/gob/dump.go
@@ -0,0 +1,22 @@
+package main
+
+// Need to compile package gob with debug.go to build this program.
+
+import (
+	"fmt"
+	"gob"
+	"os"
+)
+
+func main() {
+	var err os.Error
+	file := os.Stdin
+	if len(os.Args) > 1 {
+		file, err = os.Open(os.Args[1], os.O_RDONLY, 0)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "dump: %s\n", err)
+			os.Exit(1)
+		}
+	}
+	gob.Debug(file)
+}