AU: Class to perform delta updates.

A class to perform delta updates and the associated unittests. Also,
change the delta diff generator executable to be able to apply a
delta, which is handy for debugging.

TEST=Attached unit test, hand-tested on real build images
BUG=552

Review URL: http://codereview.chromium.org/1718001
diff --git a/subprocess_unittest.cc b/subprocess_unittest.cc
index 430f39b..86fba01 100644
--- a/subprocess_unittest.cc
+++ b/subprocess_unittest.cc
@@ -62,7 +62,7 @@
   CancelTestData* cancel_test_data = reinterpret_cast<CancelTestData*>(data);
   vector<string> cmd;
   cmd.push_back("./test_http_server");
-  uint32 tag = Subprocess::Get().Exec(cmd, CallbackBad, NULL);
+  uint32_t tag = Subprocess::Get().Exec(cmd, CallbackBad, NULL);
   EXPECT_NE(0, tag);
   cancel_test_data->spawned = true;
   printf("spawned\n");