doc: Add documentation-generating scripts to the Crashpad tree

crashpad.gyp

 # Copyright 2014 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 10 matching lines @@
       'dependencies': [
         'client/client.gyp:*',
         'compat/compat.gyp:*',
         'handler/handler.gyp:*',
         'minidump/minidump.gyp:*',
         'snapshot/snapshot.gyp:*',
         'tools/tools.gyp:*',
         'util/util.gyp:*',
       ],
       'sources': [
-        'crashpad.doxy.h',
+        'doc/crashpad.doxy.h',
         'package.h',
       ],
     },
   ],
 }