fixes #157, renaming local library identifiers if needed.

test/codegen/expect/dir/html_input_a.js

Index: test/codegen/expect/dir/html_input_a.js
diff --git a/test/codegen/expect/dir/html_input_a.js b/test/codegen/expect/dir/html_input_a.js
index d78eb67030a9d473caa118538ddb45ac4b8c30bf..7e1624c2a48230418b2077d677ce13efbaef2f17 100644
--- a/test/codegen/expect/dir/html_input_a.js
+++ b/test/codegen/expect/dir/html_input_a.js
@@ -1,5 +1,9 @@
-var html_input_a;
-(function(exports) {
+var html_input_a = dart.defineLibrary(html_input_a, {});
+var core = dart.import(core);
+var html_input_b = dart.import(html_input_b);
+var html_input_c = dart.import(html_input_c);
+var html_input_d = dart.import(html_input_d);
+(function(exports, core, html_input_b, html_input_c, html_input_d) {
   'use strict';
   // Function main: () → dynamic
   function main() {
@@ -8,4 +12,4 @@ var html_input_a;
   }
   // Exports:
   exports.main = main;
-})(html_input_a || (html_input_a = {}));
+})(html_input_a, core, html_input_b, html_input_c, html_input_d);