pkg/dartdoc: moving files around, fix library names

pkg/docgen/test/multi_library_code/lib/test_lib.dart

-library testLib;
-import 'temp2.dart';
-import 'temp3.dart';
-export 'temp2.dart';
-export 'temp3.dart';
+library test_lib;
+
+import 'test_lib_foo.dart';
+import 'test_lib_bar.dart';
+export 'test_lib_foo.dart';
+export 'test_lib_bar.dart';
 
 /**
  * Doc comment for class [A].
  *
  * Multiline Test
  */
 /*
  * Normal comment for class A.
  */
 class A {
@@ skipping 11 matching lines @@
    */
   void doThis(int A) {
     print(A);
   }
 }
 
 // A trivial use of `B` and `C` to eliminate import warnings
 B sampleMethod(C cInstance) {
   throw new UnimplementedError();
 }