test: match gccgo import error messages

Gccgo doesn't have the same equivalent of file name and
package as the gc compiler, so the error messages are
necessarily different.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/40510048

test/fixedbugs/issue5957.dir/c.go

@@ -1,12 +1,12 @@
 package p
 
 import (
-	"./a" // ERROR "imported and not used: \x22a\x22 as surprise"
-	"./b" // ERROR "imported and not used: \x22b\x22 as surprise2"
-	b "./b" // ERROR "imported and not used: \x22b\x22$"
-	foo "math" // ERROR "imported and not used: \x22math\x22 as foo"
+	"./a" // ERROR "imported and not used: \x22a\x22 as surprise|imported and not used: surprise"
+	"./b" // GC_ERROR "imported and not used: \x22b\x22 as surprise2|imported and not used: surprise2"
+	b "./b" // ERROR "imported and not used: \x22b\x22$|imported and not used: surprise2"
+	foo "math" // ERROR "imported and not used: \x22math\x22 as foo|imported and not used: math"
 	"fmt" // actually used
-	"strings" // ERROR "imported and not used: \x22strings\x22"
+	"strings" // ERROR "imported and not used: \x22strings\x22|imported and not used: strings"
 )
 
 var _ = fmt.Printf

test/import1.go

@@ -15,5 +15,5 @@ import bufio "os"	// ERROR "redeclared|redefinition|incompatible" "imported and
 import (
 	"fmt"	// GCCGO_ERROR "previous|not used"
 	fmt "math"	// ERROR "redeclared|redefinition|incompatible" "imported and not used: \x22math\x22 as fmt"
-	. "math"	// ERROR "imported and not used: \x22math\x22$"
+	. "math"	// GC_ERROR "imported and not used: \x22math\x22$"
 )

test/import4.dir/empty.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package P
+package empty
 
 import ( )
 const ( )

test/import4.dir/import4.go

@@ -18,7 +18,7 @@ import X "math"	// ERROR "imported and not used.*math"
 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"	// GC_ERROR "imported and not used.*empty"
+import Z "./empty"	// GC_ERROR "imported and not used.*empty"
 import . "./empty"	// ERROR "imported and not used.*empty"