add pkg/chrootarchive and use it on the daemon

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

Conflicts:
	builder/internals.go
	daemon/graphdriver/aufs/aufs.go
	daemon/volumes.go
		fixed conflicts in imports

reexec/command_unsupported.go

@@ -0,0 +1,11 @@
+// +build !linux
+
+package reexec
+
+import (
+	"os/exec"
+)
+
+func Command(args ...string) *exec.Cmd {
+	return nil
+}