Add gyp-generated bspatch (used by setup.exe) and bsdiff.

third_party/bsdiff/bsdiff.gyp

Index: third_party/bsdiff/bsdiff.gyp
===================================================================
--- third_party/bsdiff/bsdiff.gyp	(revision 0)
+++ third_party/bsdiff/bsdiff.gyp	(revision 0)
@@ -0,0 +1,22 @@
+# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'includes': [
+    '../../build/common.gypi',
+  ],
+  'targets': [
+    {
+      'target_name': 'bsdiff',
+      'type': 'executable',
+      'msvs_guid': 'E1D0B89E-257B-4BCA-A0C6-A2CD997A2FDC',
+      'dependencies': [
+        '../bspatch/bspatch.gyp:bspatch',
+      ],
+      'sources': [
+        'mbsdiff.cc',
+      ],
+    },
+  ],
+}