go/buildutil: rename AllPackages{,List} -> {ForEachPackage,AllPackages}.

This CL is the first refactoring automated by "gorename". :)
Though I had to update the comments and run 'hg gofmt'.   :(

LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/142930043
diff --git a/refactor/importgraph/graph.go b/refactor/importgraph/graph.go
index 922ff9f..bbf8879 100644
--- a/refactor/importgraph/graph.go
+++ b/refactor/importgraph/graph.go
@@ -88,7 +88,7 @@
 	}()
 
 	var wg sync.WaitGroup
-	buildutil.AllPackages(ctxt, func(path string, err error) {
+	buildutil.ForEachPackage(ctxt, func(path string, err error) {
 		if err != nil {
 			errorc <- pathError{path, err}
 			return