test: use testlib in a few more cases
        Introduce a new skip cmd.

R=golang-dev, bradfitz, iant, iant
CC=golang-dev
https://golang.org/cl/5868048
diff --git a/test/run.go b/test/run.go
index bf79079..ac6e3c0 100644
--- a/test/run.go
+++ b/test/run.go
@@ -1,4 +1,4 @@
-// #ignore
+// skip
 
 // Copyright 2012 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -172,7 +172,7 @@
 	donec       chan bool // closed when done
 
 	src    string
-	action string // "compile", "build", "run", "errorcheck"
+	action string // "compile", "build", "run", "errorcheck", "skip"
 
 	tempDir string
 	err     error
@@ -253,6 +253,9 @@
 		fallthrough
 	case "compile", "build", "run", "errorcheck":
 		t.action = action
+	case "skip":
+		t.action = "skip"
+		return
 	default:
 		t.err = skipError("skipped; unknown pattern: " + action)
 		t.action = "??"