cmd/compile/internal/gc: use sort.Interface for reflect methods

Generate slices of method *Sig(nature)s instead of linked lists.
Remove custom lsort function in favor of sort.Interface.

Eliminates another use of stringsCompare.

Passes go build -a -toolexec 'toolstash -cmp' std cmd.

Change-Id: I9ed1664b7f55be9e967dd7196e396a76f6ea3422
Reviewed-on: https://go-review.googlesource.com/14559
Reviewed-by: Dave Cheney <dave@cheney.net>

src/cmd/compile/internal/gc/reflect_test.go

@@ -0,0 +1,47 @@
+// Copyright 2015 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 gc
+
+import (
+	"reflect"
+	"sort"
+	"testing"
+)
+
+func TestSortingByMethodNameAndPackagePath(t *testing.T) {
+	data := []*Sig{
+		&Sig{name: "b", pkg: &Pkg{Path: "abc"}},
+		&Sig{name: "b", pkg: nil},
+		&Sig{name: "c", pkg: nil},
+		&Sig{name: "c", pkg: &Pkg{Path: "uvw"}},
+		&Sig{name: "c", pkg: nil},
+		&Sig{name: "b", pkg: &Pkg{Path: "xyz"}},
+		&Sig{name: "a", pkg: &Pkg{Path: "abc"}},
+		&Sig{name: "b", pkg: nil},
+	}
+	want := []*Sig{
+		&Sig{name: "a", pkg: &Pkg{Path: "abc"}},
+		&Sig{name: "b", pkg: nil},
+		&Sig{name: "b", pkg: nil},
+		&Sig{name: "b", pkg: &Pkg{Path: "abc"}},
+		&Sig{name: "b", pkg: &Pkg{Path: "xyz"}},
+		&Sig{name: "c", pkg: nil},
+		&Sig{name: "c", pkg: nil},
+		&Sig{name: "c", pkg: &Pkg{Path: "uvw"}},
+	}
+	if len(data) != len(want) {
+		t.Fatal("want and data must match")
+	}
+	if reflect.DeepEqual(data, want) {
+		t.Fatal("data must be shuffled")
+	}
+	sort.Sort(byMethodNameAndPackagePath(data))
+	if !reflect.DeepEqual(data, want) {
+		t.Logf("want: %#v", want)
+		t.Logf("data: %#v", data)
+		t.Errorf("sorting failed")
+	}
+
+}