The attached patches contain changes to make the feature/native-comp branch work
on Windows.

There are a few remaining issues:

* The loading process is very slow. This is especially annoying when coupled
  with autoloading. For example, autoloading Helm may stall Emacs for 5 seconds
  in my machine.

  I have thought a possible solution to this problem: load the byte-compiled
  file and put the native-compiled version in a list. Then load that list one by
  one on an idle-timer, that way the UI freezes should be minimized. This could
  reuse the "late loading" machinery implemented for deferred compilation.

* `package-delete` fails because it tries to delete the .eln file via
  `delete-file`. This is impossible in Windows because it's generally impossible
  to delete files that have an open HANDLE in the system.

  Three solutions have crossed my mind:

  - Edit `package-delete` to put the eln on a list of files that should be
    deleted when Emacs is closed.

  - Implement an unloading mechanism for native-compiled files.

  - Copy eln files to temporary files and load those temporary files instead.
    This means that deleting the original eln file is possible.

  I'd prefer the second option, but I have a semi-working patch for the third
  option.

* The `emacs_dir` environment variable needs to be set when loading the dump
  file. It is necessary for `expand-file-name`, which calls emacs_root_dir(). I
  haven't investigated why this is necessary yet. One workaround would be to use
  GetModuleFileName() to get the path to emacs.exe when `emacs_dir` is not set.