test: add testcase for gccgo compile failure

Also includes a small tweak to test/run.go to allow package names
with Unicode letters (as opposed to just ASCII chars).

Updates #27836

Change-Id: Idbf0bdea24174808cddcb69974dab820eb13e521
Reviewed-on: https://go-review.googlesource.com/138075Reviewed-by: Cherry Zhang <cherryyz@google.com>

test/fixedbugs/issue27836.dir/Äfoo.go

+package Äfoo
+
+var ÄbarV int = 101
+
+func Äbar(x int) int {
+	defer func() { ÄbarV += 3 }()
+	return Äblix(x)
+}
+
+func Äblix(x int) int {
+	defer func() { ÄbarV += 9 }()
+	return ÄbarV + x
+}

test/fixedbugs/issue27836.dir/Ämain.go

+package main
+
+import (
+	"fmt"
+
+	"./Äfoo"
+	Äblix "./Äfoo"
+)
+
+func main() {
+	fmt.Printf("Äfoo.Äbar(33) returns %v\n", Äfoo.Äbar(33))
+	fmt.Printf("Äblix.Äbar(33) returns %v\n", Äblix.Äbar(33))
+}

test/fixedbugs/issue27836.go

+// compiledir
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/run.go

@@ -321,7 +321,7 @@ func goDirFiles(longdir string) (filter []os.FileInfo, err error) {
 	return
 }
 
-var packageRE = regexp.MustCompile(`(?m)^package (\w+)`)
+var packageRE = regexp.MustCompile(`(?m)^package ([\p{Lu}\p{Ll}\w]+)`)
 
 // If singlefilepkgs is set, each file is considered a separate package
 // even if the package names are the same.