test: convert more tests to rundir/compiledir conventions

Update #4139.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6609051
diff --git a/test/import4.go b/test/import4.go
index f35f567..875bf89 100644
--- a/test/import4.go
+++ b/test/import4.go
@@ -1,7 +1,4 @@
-// $G $D/empty.go && errchk $G $D/$F.go
-
-// NOTE: This test is not run by 'run.go' and so not run by all.bash.
-// To run this test you must use the ./run shell script.
+// errorcheckdir
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -11,19 +8,4 @@
 // errors are caught by the compiler.
 // Does not compile.
 
-package main
-
-// standard
-import "fmt"	// ERROR "imported and not used.*fmt"
-
-// renamed
-import X "math"	// ERROR "imported and not used.*math"
-
-// import dot
-import . "bufio"	// ERROR "imported and not used.*bufio"
-
-// again, package without anything in it
-import "./empty"	// ERROR "imported and not used.*empty"
-import Z "./empty"	// ERROR "imported and not used.*empty"
-import . "./empty"	// ERROR "imported and not used.*empty"
-
+package ignored