Add ImmutableHeap class consisting of parts

src/vm/vm.gyp

 # Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE.md file.
 
 {
   'target_defaults': {
     'include_dirs': [
       '../../',
     ],
   },
@@ skipping 14 matching lines @@
         'event_handler_linux.cc',
         'ffi.h',
         'ffi.cc',
         'ffi_linux.cc',
         'ffi_macos.cc',
         'ffi_posix.cc',
         'fletch.cc',
         'fletch_api_impl.cc',
         'heap.cc',
         'heap_validator.cc',
+        'immutable_heap.cc',
         'gc_thread.cc',
         'interpreter.cc',
         'intrinsics.cc',
         'lookup_cache.cc',
         'natives.cc',
         'object.cc',
         'object_list.cc',
         'object_map.cc',
         'object_memory.cc',
         'port.cc',
@@ skipping 180 matching lines @@
       'target_name': 'ffi_test_library',
       'type': 'shared_library',
       'dependencies': [
       ],
       'sources': [
         'ffi_test_library.c',
       ],
     },
   ],
 }